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	$174.92	10.144%	$192.6639	$192.66	$192.65	$192.70
Purchase #2	$73.64	6.861%	$78.6924	$78.69	$78.70	$78.70
Purchase #3	$71.69	10.132%	$78.9536	$78.95	$78.95	$79.00
Purchase #4	$20.30	10.230%	$22.3767	$22.38	$22.40	$22.40
Purchase #5	$81.54	11.307%	$90.7597	$90.76	$90.75	$90.80
Purchase #6	$129.43	7.480%	$139.1114	$139.11	$139.10	$139.10
Purchase #7	$110.27	5.428%	$116.2555	$116.26	$116.25	$116.30
7 purchase totals =	$661.79		$718.8132	$718.81	$718.80	$719.00