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	$225.25	6.146%	$239.0939	$239.09	$239.10	$239.10
Purchase #2	$240.32	10.874%	$266.4524	$266.45	$266.45	$266.50
Purchase #3	$209.67	13.614%	$238.2145	$238.21	$238.20	$238.20
Purchase #4	$209.67	10.229%	$231.1171	$231.12	$231.10	$231.10
Purchase #5	$247.31	6.781%	$264.0801	$264.08	$264.10	$264.10
Purchase #6	$99.47	5.708%	$105.1477	$105.15	$105.15	$105.10
Purchase #7	$211.59	3.697%	$219.4125	$219.41	$219.40	$219.40
7 purchase totals =	$1,443.28		$1,563.5182	$1,563.51	$1,563.50	$1,563.50