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	$185.31	11.653%	$206.9042	$206.90	$206.90	$206.90
Purchase #2	$235.30	11.120%	$261.4654	$261.47	$261.45	$261.50
Purchase #3	$156.75	5.842%	$165.9073	$165.91	$165.90	$165.90
Purchase #4	$142.47	12.527%	$160.3172	$160.32	$160.30	$160.30
Purchase #5	$190.72	12.823%	$215.176	$215.18	$215.20	$215.20
Purchase #6	$50.84	6.166%	$53.9748	$53.97	$53.95	$54.00
Purchase #7	$183.30	3.554%	$189.8145	$189.81	$189.80	$189.80
7 purchase totals =	$1,144.69		$1,253.5594	$1,253.56	$1,253.50	$1,253.60