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	$188.93	8.256%	$204.5281	$204.53	$204.55	$204.50
Purchase #2	$99.71	4.216%	$103.9138	$103.91	$103.90	$103.90
Purchase #3	$131.65	13.164%	$148.9804	$148.98	$149.00	$149.00
Purchase #4	$192.89	13.164%	$218.282	$218.28	$218.30	$218.30
Purchase #5	$91.84	9.136%	$100.2305	$100.23	$100.25	$100.20
Purchase #6	$194.98	12.350%	$219.06	$219.06	$219.05	$219.10
Purchase #7	$148.41	6.681%	$158.3253	$158.33	$158.35	$158.30
7 purchase totals =	$1,048.41		$1,153.3201	$1,153.32	$1,153.40	$1,153.30