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	$52.55	4.788%	$55.0661	$55.07	$55.05	$55.10
Purchase #2	$168.55	5.810%	$178.3428	$178.34	$178.35	$178.30
Purchase #3	$153.41	7.805%	$165.3837	$165.38	$165.40	$165.40
Purchase #4	$41.36	11.302%	$46.0345	$46.03	$46.05	$46.00
Purchase #5	$111.38	13.275%	$126.1657	$126.17	$126.15	$126.20
Purchase #6	$121.48	8.103%	$131.3235	$131.32	$131.30	$131.30
Purchase #7	$54.73	10.669%	$60.5691	$60.57	$60.55	$60.60
7 purchase totals =	$703.46		$762.8854	$762.88	$762.85	$762.90