Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$158.35	4.251%	$165.0815	$165.08	$165.10	$165.10
Purchase #2	$145.77	13.627%	$165.6341	$165.63	$165.65	$165.60
Purchase #3	$165.33	10.278%	$182.3226	$182.32	$182.30	$182.30
Purchase #4	$141.79	10.850%	$157.1742	$157.17	$157.15	$157.20
Purchase #5	$156.59	7.209%	$167.8786	$167.88	$167.90	$167.90
Purchase #6	$130.54	3.239%	$134.7682	$134.77	$134.75	$134.80
Purchase #7	$114.69	13.771%	$130.484	$130.48	$130.50	$130.50
7 purchase totals =	$1,013.06		$1,103.3432	$1,103.33	$1,103.35	$1,103.40