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	$104.75	6.501%	$111.5598	$111.56	$111.55	$111.60
Purchase #2	$134.54	9.438%	$147.2379	$147.24	$147.25	$147.20
Purchase #3	$57.37	4.493%	$59.9476	$59.95	$59.95	$59.90
Purchase #4	$32.64	8.316%	$35.3543	$35.35	$35.35	$35.40
Purchase #5	$48.59	11.301%	$54.0812	$54.08	$54.10	$54.10
Purchase #6	$212.96	12.126%	$238.7835	$238.78	$238.80	$238.80
Purchase #7	$42.62	9.668%	$46.7405	$46.74	$46.75	$46.70
7 purchase totals =	$633.47		$693.7048	$693.70	$693.75	$693.70