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	$108.67	13.284%	$123.1057	$123.11	$123.10	$123.10
Purchase #2	$152.30	9.844%	$167.2924	$167.29	$167.30	$167.30
Purchase #3	$223.50	13.654%	$254.0167	$254.02	$254.00	$254.00
Purchase #4	$191.53	8.326%	$207.4768	$207.48	$207.50	$207.50
Purchase #5	$76.80	8.274%	$83.1544	$83.15	$83.15	$83.20
Purchase #6	$75.69	3.826%	$78.5859	$78.59	$78.60	$78.60
Purchase #7	$152.52	10.619%	$168.7161	$168.72	$168.70	$168.70
7 purchase totals =	$981.01		$1,082.3480	$1,082.36	$1,082.35	$1,082.40