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	$35.91	5.672%	$37.9468	$37.95	$37.95	$37.90
Purchase #2	$241.69	4.607%	$252.8247	$252.82	$252.80	$252.80
Purchase #3	$134.73	5.727%	$142.446	$142.45	$142.45	$142.40
Purchase #4	$109.83	6.363%	$116.8185	$116.82	$116.80	$116.80
Purchase #5	$228.72	13.816%	$260.32	$260.32	$260.30	$260.30
Purchase #6	$99.39	13.345%	$112.6536	$112.65	$112.65	$112.70
Purchase #7	$177.76	6.519%	$189.3482	$189.35	$189.35	$189.30
7 purchase totals =	$1,028.03		$1,112.3578	$1,112.36	$1,112.30	$1,112.20