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	$98.65	13.700%	$112.1651	$112.17	$112.15	$112.20
Purchase #2	$77.54	12.651%	$87.3496	$87.35	$87.35	$87.30
Purchase #3	$61.51	4.435%	$64.238	$64.24	$64.25	$64.20
Purchase #4	$115.92	13.443%	$131.5031	$131.50	$131.50	$131.50
Purchase #5	$244.60	12.780%	$275.8599	$275.86	$275.85	$275.90
Purchase #6	$125.77	4.220%	$131.0775	$131.08	$131.10	$131.10
Purchase #7	$143.27	12.420%	$161.0641	$161.06	$161.05	$161.10
7 purchase totals =	$867.26		$963.2573	$963.26	$963.25	$963.30