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	$95.75	11.305%	$106.5745	$106.57	$106.55	$106.60
Purchase #2	$101.90	8.582%	$110.6451	$110.65	$110.65	$110.60
Purchase #3	$32.79	13.845%	$37.3298	$37.33	$37.35	$37.30
Purchase #4	$246.65	4.109%	$256.7848	$256.78	$256.80	$256.80
Purchase #5	$88.98	7.176%	$95.3652	$95.37	$95.35	$95.40
Purchase #6	$79.72	8.276%	$86.3176	$86.32	$86.30	$86.30
Purchase #7	$190.43	4.257%	$198.5366	$198.54	$198.55	$198.50
7 purchase totals =	$836.22		$891.5536	$891.56	$891.55	$891.50