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	$52.45	12.305%	$58.904	$58.90	$58.90	$58.90
Purchase #2	$54.40	9.297%	$59.4576	$59.46	$59.45	$59.50
Purchase #3	$221.80	6.183%	$235.5139	$235.51	$235.50	$235.50
Purchase #4	$243.29	11.591%	$271.4897	$271.49	$271.50	$271.50
Purchase #5	$174.78	11.506%	$194.8902	$194.89	$194.90	$194.90
Purchase #6	$199.91	6.613%	$213.13	$213.13	$213.15	$213.10
Purchase #7	$156.85	10.572%	$173.4322	$173.43	$173.45	$173.40
7 purchase totals =	$1,103.48		$1,206.8176	$1,206.81	$1,206.85	$1,206.80