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	$243.81	3.190%	$251.5875	$251.59	$251.60	$251.60
Purchase #2	$168.95	9.651%	$185.2554	$185.26	$185.25	$185.30
Purchase #3	$105.72	13.636%	$120.136	$120.14	$120.15	$120.10
Purchase #4	$178.96	5.550%	$188.8923	$188.89	$188.90	$188.90
Purchase #5	$32.96	10.132%	$36.2995	$36.30	$36.30	$36.30
Purchase #6	$108.72	6.607%	$115.9031	$115.90	$115.90	$115.90
Purchase #7	$221.66	11.362%	$246.845	$246.85	$246.85	$246.80
7 purchase totals =	$1,060.78		$1,144.9188	$1,144.93	$1,144.95	$1,144.90