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	$151.88	10.770%	$168.2375	$168.24	$168.25	$168.20
Purchase #2	$142.50	10.799%	$157.8886	$157.89	$157.90	$157.90
Purchase #3	$218.54	4.286%	$227.9066	$227.91	$227.90	$227.90
Purchase #4	$78.74	8.114%	$85.129	$85.13	$85.15	$85.10
Purchase #5	$169.75	11.533%	$189.3273	$189.33	$189.35	$189.30
Purchase #6	$163.80	11.198%	$182.1423	$182.14	$182.15	$182.10
Purchase #7	$124.86	6.865%	$133.4316	$133.43	$133.45	$133.40
7 purchase totals =	$1,050.07		$1,144.0629	$1,144.07	$1,144.15	$1,143.90