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	$46.27	13.532%	$52.5313	$52.53	$52.55	$52.50
Purchase #2	$119.82	6.412%	$127.5029	$127.50	$127.50	$127.50
Purchase #3	$64.82	5.419%	$68.3326	$68.33	$68.35	$68.30
Purchase #4	$22.62	11.847%	$25.2998	$25.30	$25.30	$25.30
Purchase #5	$86.69	9.530%	$94.9516	$94.95	$94.95	$95.00
Purchase #6	$155.77	7.202%	$166.9886	$166.99	$167.00	$167.00
Purchase #7	$99.34	4.801%	$104.1093	$104.11	$104.10	$104.10
7 purchase totals =	$595.33		$639.7161	$639.71	$639.75	$639.70