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	$104.28	8.705%	$113.3576	$113.36	$113.35	$113.40
Purchase #2	$107.92	7.810%	$116.3486	$116.35	$116.35	$116.30
Purchase #3	$157.32	11.647%	$175.6431	$175.64	$175.65	$175.60
Purchase #4	$166.83	7.563%	$179.4474	$179.45	$179.45	$179.40
Purchase #5	$42.39	6.406%	$45.1055	$45.11	$45.10	$45.10
Purchase #6	$237.90	5.190%	$250.247	$250.25	$250.25	$250.20
Purchase #7	$42.87	6.873%	$45.8165	$45.82	$45.80	$45.80
7 purchase totals =	$859.51		$925.9657	$925.98	$925.95	$925.80