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	$95.25	9.793%	$104.5778	$104.58	$104.60	$104.60
Purchase #2	$230.27	13.578%	$261.5361	$261.54	$261.55	$261.50
Purchase #3	$57.68	11.673%	$64.413	$64.41	$64.40	$64.40
Purchase #4	$211.41	8.103%	$228.5406	$228.54	$228.55	$228.50
Purchase #5	$247.82	10.290%	$273.3207	$273.32	$273.30	$273.30
Purchase #6	$46.98	3.199%	$48.4829	$48.48	$48.50	$48.50
Purchase #7	$56.80	4.523%	$59.3691	$59.37	$59.35	$59.40
7 purchase totals =	$946.21		$1,040.2402	$1,040.24	$1,040.25	$1,040.20