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	$224.73	8.198%	$243.1534	$243.15	$243.15	$243.20
Purchase #2	$169.83	8.869%	$184.8922	$184.89	$184.90	$184.90
Purchase #3	$18.43	6.290%	$19.5892	$19.59	$19.60	$19.60
Purchase #4	$189.38	5.263%	$199.3471	$199.35	$199.35	$199.30
Purchase #5	$100.58	4.700%	$105.3073	$105.31	$105.30	$105.30
Purchase #6	$242.46	8.845%	$263.9056	$263.91	$263.90	$263.90
Purchase #7	$59.55	6.374%	$63.3457	$63.35	$63.35	$63.30
7 purchase totals =	$1,004.96		$1,079.5405	$1,079.55	$1,079.55	$1,079.50