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	$138.64	7.472%	$148.9992	$149.00	$149.00	$149.00
Purchase #2	$48.40	6.503%	$51.5475	$51.55	$51.55	$51.50
Purchase #3	$180.79	4.259%	$188.4898	$188.49	$188.50	$188.50
Purchase #4	$79.92	7.450%	$85.874	$85.87	$85.85	$85.90
Purchase #5	$233.27	4.292%	$243.2819	$243.28	$243.30	$243.30
Purchase #6	$218.46	13.718%	$248.4283	$248.43	$248.45	$248.40
Purchase #7	$91.70	8.563%	$99.5523	$99.55	$99.55	$99.60
7 purchase totals =	$991.18		$1,066.1730	$1,066.17	$1,066.20	$1,066.20