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	$176.42	9.735%	$193.5945	$193.59	$193.60	$193.60
Purchase #2	$226.83	11.606%	$253.1559	$253.16	$253.15	$253.20
Purchase #3	$238.28	11.503%	$265.6893	$265.69	$265.70	$265.70
Purchase #4	$61.38	9.469%	$67.1921	$67.19	$67.20	$67.20
Purchase #5	$99.33	4.440%	$103.7403	$103.74	$103.75	$103.70
Purchase #6	$54.92	4.688%	$57.4946	$57.49	$57.50	$57.50
Purchase #7	$195.25	7.392%	$209.6829	$209.68	$209.70	$209.70
7 purchase totals =	$1,052.41		$1,150.5496	$1,150.54	$1,150.60	$1,150.60