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	$35.34	10.155%	$38.9288	$38.93	$38.95	$38.90
Purchase #2	$185.43	3.294%	$191.5381	$191.54	$191.55	$191.50
Purchase #3	$212.65	13.152%	$240.6177	$240.62	$240.60	$240.60
Purchase #4	$51.62	11.757%	$57.689	$57.69	$57.70	$57.70
Purchase #5	$183.40	3.767%	$190.3087	$190.31	$190.30	$190.30
Purchase #6	$153.54	8.460%	$166.5295	$166.53	$166.55	$166.50
Purchase #7	$156.28	3.730%	$162.1092	$162.11	$162.10	$162.10
7 purchase totals =	$978.26		$1,047.7210	$1,047.73	$1,047.75	$1,047.60