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	$247.40	10.441%	$273.231	$273.23	$273.25	$273.20
Purchase #2	$95.33	4.846%	$99.9497	$99.95	$99.95	$99.90
Purchase #3	$124.48	13.298%	$141.0334	$141.03	$141.05	$141.00
Purchase #4	$133.30	10.340%	$147.0832	$147.08	$147.10	$147.10
Purchase #5	$55.97	6.568%	$59.6461	$59.65	$59.65	$59.60
Purchase #6	$41.58	5.342%	$43.8012	$43.80	$43.80	$43.80
Purchase #7	$218.26	9.430%	$238.8419	$238.84	$238.85	$238.80
7 purchase totals =	$916.32		$1,003.5865	$1,003.58	$1,003.65	$1,003.40