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	$181.61	4.383%	$189.57	$189.57	$189.55	$189.60
Purchase #2	$104.98	4.317%	$109.512	$109.51	$109.50	$109.50
Purchase #3	$74.70	3.760%	$77.5087	$77.51	$77.50	$77.50
Purchase #4	$35.25	6.516%	$37.5469	$37.55	$37.55	$37.50
Purchase #5	$21.72	3.203%	$22.4157	$22.42	$22.40	$22.40
Purchase #6	$121.92	8.421%	$132.1869	$132.19	$132.20	$132.20
Purchase #7	$129.76	11.374%	$144.5189	$144.52	$144.50	$144.50
7 purchase totals =	$669.94		$713.2591	$713.27	$713.20	$713.20