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	$240.28	13.172%	$271.9297	$271.93	$271.95	$271.90
Purchase #2	$154.60	13.214%	$175.0288	$175.03	$175.05	$175.00
Purchase #3	$57.86	6.438%	$61.585	$61.59	$61.60	$61.60
Purchase #4	$16.76	11.615%	$18.7067	$18.71	$18.70	$18.70
Purchase #5	$115.36	7.317%	$123.8009	$123.80	$123.80	$123.80
Purchase #6	$138.72	12.767%	$156.4304	$156.43	$156.45	$156.40
Purchase #7	$224.72	12.707%	$253.2752	$253.28	$253.30	$253.30
7 purchase totals =	$948.30		$1,060.7567	$1,060.77	$1,060.85	$1,060.70