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	$232.86	7.598%	$250.5527	$250.55	$250.55	$250.60
Purchase #2	$30.77	7.781%	$33.1642	$33.16	$33.15	$33.20
Purchase #3	$162.97	3.237%	$168.2453	$168.25	$168.25	$168.20
Purchase #4	$235.30	5.796%	$248.938	$248.94	$248.95	$248.90
Purchase #5	$54.81	12.862%	$61.8597	$61.86	$61.85	$61.90
Purchase #6	$164.48	3.324%	$169.9473	$169.95	$169.95	$169.90
Purchase #7	$106.59	7.717%	$114.8156	$114.82	$114.80	$114.80
7 purchase totals =	$987.78		$1,047.5228	$1,047.53	$1,047.50	$1,047.50