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	$93.58	7.502%	$100.6004	$100.60	$100.60	$100.60
Purchase #2	$249.43	6.364%	$265.3037	$265.30	$265.30	$265.30
Purchase #3	$56.65	8.231%	$61.3129	$61.31	$61.30	$61.30
Purchase #4	$75.65	9.200%	$82.6098	$82.61	$82.60	$82.60
Purchase #5	$80.83	12.229%	$90.7147	$90.71	$90.70	$90.70
Purchase #6	$197.59	3.333%	$204.1757	$204.18	$204.20	$204.20
Purchase #7	$52.59	12.703%	$59.2705	$59.27	$59.25	$59.30
7 purchase totals =	$806.32		$863.9877	$863.98	$863.95	$864.00