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	$236.36	3.237%	$244.011	$244.01	$244.00	$244.00
Purchase #2	$151.48	5.152%	$159.2842	$159.28	$159.30	$159.30
Purchase #3	$126.56	6.258%	$134.4801	$134.48	$134.50	$134.50
Purchase #4	$126.25	9.234%	$137.9079	$137.91	$137.90	$137.90
Purchase #5	$227.61	10.851%	$252.308	$252.31	$252.30	$252.30
Purchase #6	$80.88	10.534%	$89.3999	$89.40	$89.40	$89.40
Purchase #7	$29.68	9.649%	$32.5438	$32.54	$32.55	$32.50
7 purchase totals =	$978.82		$1,049.9349	$1,049.93	$1,049.95	$1,049.90