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	$70.74	4.421%	$73.8674	$73.87	$73.85	$73.90
Purchase #2	$75.56	12.650%	$85.1183	$85.12	$85.10	$85.10
Purchase #3	$125.64	13.684%	$142.8326	$142.83	$142.85	$142.80
Purchase #4	$227.40	4.376%	$237.351	$237.35	$237.35	$237.40
Purchase #5	$83.91	6.834%	$89.6444	$89.64	$89.65	$89.60
Purchase #6	$54.83	11.784%	$61.2912	$61.29	$61.30	$61.30
Purchase #7	$183.41	9.321%	$200.5056	$200.51	$200.50	$200.50
7 purchase totals =	$821.49		$890.6105	$890.61	$890.60	$890.60