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	$217.29	11.713%	$242.7412	$242.74	$242.75	$242.70
Purchase #2	$72.29	8.124%	$78.1628	$78.16	$78.15	$78.20
Purchase #3	$103.98	7.581%	$111.8627	$111.86	$111.85	$111.90
Purchase #4	$191.50	13.867%	$218.0553	$218.06	$218.05	$218.10
Purchase #5	$10.51	6.428%	$11.1856	$11.19	$11.20	$11.20
Purchase #6	$247.33	8.377%	$268.0488	$268.05	$268.05	$268.00
Purchase #7	$61.79	7.212%	$66.2463	$66.25	$66.25	$66.20
7 purchase totals =	$904.69		$996.3027	$996.31	$996.30	$996.30