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	$64.73	10.524%	$71.5422	$71.54	$71.55	$71.50
Purchase #2	$79.70	13.352%	$90.3415	$90.34	$90.35	$90.30
Purchase #3	$205.40	7.211%	$220.2114	$220.21	$220.20	$220.20
Purchase #4	$97.83	12.337%	$109.8993	$109.90	$109.90	$109.90
Purchase #5	$239.43	3.812%	$248.5571	$248.56	$248.55	$248.60
Purchase #6	$154.68	7.841%	$166.8085	$166.81	$166.80	$166.80
Purchase #7	$220.76	10.802%	$244.6065	$244.61	$244.60	$244.60
7 purchase totals =	$1,062.53		$1,151.9665	$1,151.97	$1,151.95	$1,151.90