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	$164.47	4.157%	$171.307	$171.31	$171.30	$171.30
Purchase #2	$158.66	6.567%	$169.0792	$169.08	$169.10	$169.10
Purchase #3	$113.34	13.666%	$128.829	$128.83	$128.85	$128.80
Purchase #4	$103.86	13.130%	$117.4968	$117.50	$117.50	$117.50
Purchase #5	$88.50	12.168%	$99.2687	$99.27	$99.25	$99.30
Purchase #6	$74.89	4.510%	$78.2675	$78.27	$78.25	$78.30
Purchase #7	$53.72	9.337%	$58.7358	$58.74	$58.75	$58.70
7 purchase totals =	$757.44		$822.9840	$823.00	$823.00	$823.00