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	$155.62	9.125%	$169.8203	$169.82	$169.80	$169.80
Purchase #2	$19.78	3.741%	$20.52	$20.52	$20.50	$20.50
Purchase #3	$192.76	11.804%	$215.5134	$215.51	$215.50	$215.50
Purchase #4	$92.48	13.356%	$104.8316	$104.83	$104.85	$104.80
Purchase #5	$171.60	9.615%	$188.0993	$188.10	$188.10	$188.10
Purchase #6	$206.28	4.755%	$216.0886	$216.09	$216.10	$216.10
Purchase #7	$215.56	6.861%	$230.3496	$230.35	$230.35	$230.30
7 purchase totals =	$1,054.08		$1,145.2228	$1,145.22	$1,145.20	$1,145.10