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	$58.96	4.488%	$61.6061	$61.61	$61.60	$61.60
Purchase #2	$68.68	11.275%	$76.4237	$76.42	$76.40	$76.40
Purchase #3	$7.72	7.627%	$8.3088	$8.31	$8.30	$8.30
Purchase #4	$62.41	4.178%	$65.0175	$65.02	$65.00	$65.00
Purchase #5	$96.51	12.349%	$108.428	$108.43	$108.45	$108.40
Purchase #6	$83.27	11.571%	$92.9052	$92.91	$92.90	$92.90
Purchase #7	$181.77	4.779%	$190.4568	$190.46	$190.45	$190.50
7 purchase totals =	$559.32		$603.1461	$603.16	$603.10	$603.10