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	$46.90	11.794%	$52.4314	$52.43	$52.45	$52.40
Purchase #2	$58.70	5.368%	$61.851	$61.85	$61.85	$61.90
Purchase #3	$119.87	8.729%	$130.3335	$130.33	$130.35	$130.30
Purchase #4	$235.71	12.780%	$265.8337	$265.83	$265.85	$265.80
Purchase #5	$195.34	12.642%	$220.0349	$220.03	$220.05	$220.00
Purchase #6	$69.71	12.817%	$78.6447	$78.64	$78.65	$78.60
Purchase #7	$229.72	6.717%	$245.1503	$245.15	$245.15	$245.20
7 purchase totals =	$955.95		$1,054.2795	$1,054.26	$1,054.35	$1,054.20