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	$90.34	6.286%	$96.0188	$96.02	$96.00	$96.00
Purchase #2	$119.44	10.423%	$131.8892	$131.89	$131.90	$131.90
Purchase #3	$35.36	6.682%	$37.7228	$37.72	$37.70	$37.70
Purchase #4	$196.84	4.423%	$205.5462	$205.55	$205.55	$205.50
Purchase #5	$53.40	10.523%	$59.0193	$59.02	$59.00	$59.00
Purchase #6	$140.30	5.810%	$148.4514	$148.45	$148.45	$148.50
Purchase #7	$215.86	6.111%	$229.0512	$229.05	$229.05	$229.10
7 purchase totals =	$851.54		$907.6989	$907.70	$907.65	$907.70