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	$57.98	5.246%	$61.0216	$61.02	$61.00	$61.00
Purchase #2	$44.88	13.194%	$50.8015	$50.80	$50.80	$50.80
Purchase #3	$174.43	3.203%	$180.017	$180.02	$180.00	$180.00
Purchase #4	$188.38	9.311%	$205.9201	$205.92	$205.90	$205.90
Purchase #5	$60.30	7.406%	$64.7658	$64.77	$64.75	$64.80
Purchase #6	$79.73	8.407%	$86.4329	$86.43	$86.45	$86.40
Purchase #7	$85.89	8.180%	$92.9158	$92.92	$92.90	$92.90
7 purchase totals =	$691.59		$741.8747	$741.88	$741.80	$741.80