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	$167.30	10.495%	$184.8581	$184.86	$184.85	$184.90
Purchase #2	$59.36	7.122%	$63.5876	$63.59	$63.60	$63.60
Purchase #3	$153.93	7.215%	$165.036	$165.04	$165.05	$165.00
Purchase #4	$120.39	5.637%	$127.1764	$127.18	$127.20	$127.20
Purchase #5	$111.95	7.629%	$120.4907	$120.49	$120.50	$120.50
Purchase #6	$19.81	12.760%	$22.3378	$22.34	$22.35	$22.30
Purchase #7	$90.72	6.481%	$96.5996	$96.60	$96.60	$96.60
7 purchase totals =	$723.46		$780.0862	$780.10	$780.15	$780.10