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	$151.50	11.443%	$168.8361	$168.84	$168.85	$168.80
Purchase #2	$163.28	12.259%	$183.2965	$183.30	$183.30	$183.30
Purchase #3	$61.87	8.523%	$67.1432	$67.14	$67.15	$67.10
Purchase #4	$240.69	12.554%	$270.9062	$270.91	$270.90	$270.90
Purchase #5	$240.52	3.390%	$248.6736	$248.67	$248.65	$248.70
Purchase #6	$40.81	13.516%	$46.3259	$46.33	$46.35	$46.30
Purchase #7	$61.40	7.651%	$66.0977	$66.10	$66.10	$66.10
7 purchase totals =	$960.07		$1,051.2792	$1,051.29	$1,051.30	$1,051.20