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	$160.84	7.179%	$172.3867	$172.39	$172.40	$172.40
Purchase #2	$16.44	4.801%	$17.2293	$17.23	$17.25	$17.20
Purchase #3	$174.42	4.605%	$182.452	$182.45	$182.45	$182.50
Purchase #4	$27.30	12.655%	$30.7548	$30.75	$30.75	$30.80
Purchase #5	$94.38	11.568%	$105.2979	$105.30	$105.30	$105.30
Purchase #6	$10.66	12.356%	$11.9771	$11.98	$12.00	$12.00
Purchase #7	$42.32	6.620%	$45.1216	$45.12	$45.10	$45.10
7 purchase totals =	$526.36		$565.2194	$565.22	$565.25	$565.30