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	$8.52	3.349%	$8.8053	$8.81	$8.80	$8.80
Purchase #2	$213.83	4.362%	$223.1573	$223.16	$223.15	$223.20
Purchase #3	$248.69	8.739%	$270.423	$270.42	$270.40	$270.40
Purchase #4	$78.55	12.770%	$88.5808	$88.58	$88.60	$88.60
Purchase #5	$170.32	7.809%	$183.6203	$183.62	$183.60	$183.60
Purchase #6	$105.75	5.751%	$111.8317	$111.83	$111.85	$111.80
Purchase #7	$140.85	13.649%	$160.0746	$160.07	$160.05	$160.10
7 purchase totals =	$966.51		$1,046.4930	$1,046.49	$1,046.45	$1,046.50