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	$137.75	9.137%	$150.3362	$150.34	$150.35	$150.30
Purchase #2	$162.63	6.710%	$173.5425	$173.54	$173.55	$173.50
Purchase #3	$42.78	13.281%	$48.4616	$48.46	$48.45	$48.50
Purchase #4	$203.27	5.647%	$214.7487	$214.75	$214.75	$214.70
Purchase #5	$243.94	8.353%	$264.3163	$264.32	$264.30	$264.30
Purchase #6	$86.49	3.389%	$89.4211	$89.42	$89.40	$89.40
Purchase #7	$76.77	11.367%	$85.4964	$85.50	$85.50	$85.50
7 purchase totals =	$953.63		$1,026.3228	$1,026.33	$1,026.30	$1,026.20