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	$30.91	7.787%	$33.317	$33.32	$33.30	$33.30
Purchase #2	$104.53	6.192%	$111.0025	$111.00	$111.00	$111.00
Purchase #3	$55.66	6.510%	$59.2835	$59.28	$59.30	$59.30
Purchase #4	$185.25	3.297%	$191.3577	$191.36	$191.35	$191.40
Purchase #5	$41.89	11.818%	$46.8406	$46.84	$46.85	$46.80
Purchase #6	$176.30	4.793%	$184.7501	$184.75	$184.75	$184.80
Purchase #7	$23.27	6.361%	$24.7502	$24.75	$24.75	$24.80
7 purchase totals =	$617.81		$651.3016	$651.30	$651.30	$651.40