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	$133.45	10.735%	$147.7759	$147.78	$147.80	$147.80
Purchase #2	$5.90	3.589%	$6.1118	$6.11	$6.10	$6.10
Purchase #3	$217.76	11.702%	$243.2423	$243.24	$243.25	$243.20
Purchase #4	$175.57	7.592%	$188.8993	$188.90	$188.90	$188.90
Purchase #5	$57.47	4.282%	$59.9309	$59.93	$59.95	$59.90
Purchase #6	$150.36	13.611%	$170.8255	$170.83	$170.85	$170.80
Purchase #7	$229.36	6.657%	$244.6285	$244.63	$244.65	$244.60
7 purchase totals =	$969.87		$1,061.4142	$1,061.42	$1,061.50	$1,061.30