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	$153.44	9.675%	$168.2853	$168.29	$168.30	$168.30
Purchase #2	$118.54	3.791%	$123.0339	$123.03	$123.05	$123.00
Purchase #3	$130.89	5.835%	$138.5274	$138.53	$138.55	$138.50
Purchase #4	$181.95	10.542%	$201.1312	$201.13	$201.15	$201.10
Purchase #5	$199.32	10.443%	$220.135	$220.14	$220.15	$220.10
Purchase #6	$112.31	9.836%	$123.3568	$123.36	$123.35	$123.40
Purchase #7	$96.72	10.345%	$106.7257	$106.73	$106.75	$106.70
7 purchase totals =	$993.17		$1,081.1953	$1,081.21	$1,081.30	$1,081.10