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	$176.85	4.518%	$184.8401	$184.84	$184.85	$184.80
Purchase #2	$181.30	12.334%	$203.6615	$203.66	$203.65	$203.70
Purchase #3	$100.55	10.547%	$111.155	$111.16	$111.15	$111.20
Purchase #4	$89.48	3.454%	$92.5706	$92.57	$92.55	$92.60
Purchase #5	$250.72	6.645%	$267.3803	$267.38	$267.40	$267.40
Purchase #6	$69.62	10.428%	$76.88	$76.88	$76.90	$76.90
Purchase #7	$152.38	12.726%	$171.7719	$171.77	$171.75	$171.80
7 purchase totals =	$1,020.90		$1,108.2594	$1,108.26	$1,108.25	$1,108.40