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	$152.75	12.838%	$172.36	$172.36	$172.35	$172.40
Purchase #2	$212.46	5.384%	$223.8988	$223.90	$223.90	$223.90
Purchase #3	$54.34	9.749%	$59.6376	$59.64	$59.65	$59.60
Purchase #4	$169.42	12.746%	$191.0143	$191.01	$191.00	$191.00
Purchase #5	$128.32	10.289%	$141.5228	$141.52	$141.50	$141.50
Purchase #6	$139.83	9.515%	$153.1348	$153.13	$153.15	$153.10
Purchase #7	$56.42	4.755%	$59.1028	$59.10	$59.10	$59.10
7 purchase totals =	$913.54		$1,000.6711	$1,000.66	$1,000.65	$1,000.60