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	$149.88	5.631%	$158.3197	$158.32	$158.30	$158.30
Purchase #2	$250.71	3.663%	$259.8935	$259.89	$259.90	$259.90
Purchase #3	$120.39	3.642%	$124.7746	$124.77	$124.75	$124.80
Purchase #4	$29.35	10.797%	$32.5189	$32.52	$32.50	$32.50
Purchase #5	$166.27	12.169%	$186.5034	$186.50	$186.50	$186.50
Purchase #6	$28.32	10.562%	$31.3112	$31.31	$31.30	$31.30
Purchase #7	$148.63	4.819%	$155.7925	$155.79	$155.80	$155.80
7 purchase totals =	$893.55		$949.1138	$949.10	$949.05	$949.10