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	$50.62	6.616%	$53.969	$53.97	$53.95	$54.00
Purchase #2	$188.74	10.443%	$208.4501	$208.45	$208.45	$208.50
Purchase #3	$100.89	13.734%	$114.7462	$114.75	$114.75	$114.70
Purchase #4	$183.30	7.282%	$196.6479	$196.65	$196.65	$196.60
Purchase #5	$210.33	9.196%	$229.6719	$229.67	$229.65	$229.70
Purchase #6	$26.32	10.806%	$29.1641	$29.16	$29.15	$29.20
Purchase #7	$160.73	6.550%	$171.2578	$171.26	$171.25	$171.30
7 purchase totals =	$920.93		$1,003.9070	$1,003.91	$1,003.85	$1,004.00