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	$223.41	10.794%	$247.5249	$247.52	$247.50	$247.50
Purchase #2	$92.91	12.276%	$104.3156	$104.32	$104.30	$104.30
Purchase #3	$100.43	3.677%	$104.1228	$104.12	$104.10	$104.10
Purchase #4	$56.34	13.769%	$64.0975	$64.10	$64.10	$64.10
Purchase #5	$161.73	6.663%	$172.5061	$172.51	$172.50	$172.50
Purchase #6	$249.28	3.460%	$257.9051	$257.91	$257.90	$257.90
Purchase #7	$134.63	5.302%	$141.7681	$141.77	$141.75	$141.80
7 purchase totals =	$1,018.73		$1,092.2401	$1,092.25	$1,092.15	$1,092.20