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	$111.62	10.834%	$123.7129	$123.71	$123.70	$123.70
Purchase #2	$25.99	4.317%	$27.112	$27.11	$27.10	$27.10
Purchase #3	$135.58	4.287%	$141.3923	$141.39	$141.40	$141.40
Purchase #4	$35.91	4.724%	$37.6064	$37.61	$37.60	$37.60
Purchase #5	$158.29	12.784%	$178.5258	$178.53	$178.55	$178.50
Purchase #6	$140.67	6.250%	$149.4619	$149.46	$149.45	$149.50
Purchase #7	$26.50	10.579%	$29.3034	$29.30	$29.30	$29.30
7 purchase totals =	$634.56		$687.1147	$687.11	$687.10	$687.10