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	$165.33	5.428%	$174.3041	$174.30	$174.30	$174.30
Purchase #2	$92.36	8.810%	$100.4969	$100.50	$100.50	$100.50
Purchase #3	$103.99	7.792%	$112.0929	$112.09	$112.10	$112.10
Purchase #4	$117.55	10.782%	$130.2242	$130.22	$130.20	$130.20
Purchase #5	$236.78	11.489%	$263.9837	$263.98	$264.00	$264.00
Purchase #6	$105.98	3.564%	$109.7571	$109.76	$109.75	$109.80
Purchase #7	$208.74	4.842%	$218.8472	$218.85	$218.85	$218.80
7 purchase totals =	$1,030.73		$1,109.7061	$1,109.70	$1,109.70	$1,109.70