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	$187.63	6.709%	$200.2181	$200.22	$200.20	$200.20
Purchase #2	$60.54	10.276%	$66.7611	$66.76	$66.75	$66.80
Purchase #3	$50.36	3.391%	$52.0677	$52.07	$52.05	$52.10
Purchase #4	$53.37	5.528%	$56.3203	$56.32	$56.30	$56.30
Purchase #5	$42.89	9.319%	$46.8869	$46.89	$46.90	$46.90
Purchase #6	$120.79	5.591%	$127.5434	$127.54	$127.55	$127.50
Purchase #7	$245.83	12.812%	$277.3257	$277.33	$277.35	$277.30
7 purchase totals =	$761.41		$827.1232	$827.13	$827.10	$827.10