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	$154.71	9.152%	$168.8691	$168.87	$168.85	$168.90
Purchase #2	$15.44	11.154%	$17.1622	$17.16	$17.15	$17.20
Purchase #3	$123.69	9.248%	$135.1289	$135.13	$135.15	$135.10
Purchase #4	$106.98	4.535%	$111.8315	$111.83	$111.85	$111.80
Purchase #5	$215.43	10.702%	$238.4853	$238.49	$238.50	$238.50
Purchase #6	$165.48	11.308%	$184.1925	$184.19	$184.20	$184.20
Purchase #7	$148.43	11.826%	$165.9833	$165.98	$166.00	$166.00
7 purchase totals =	$930.16		$1,021.6528	$1,021.65	$1,021.70	$1,021.70