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	$172.76	10.297%	$190.5491	$190.55	$190.55	$190.50
Purchase #2	$138.92	6.867%	$148.4596	$148.46	$148.45	$148.50
Purchase #3	$219.92	12.830%	$248.1357	$248.14	$248.15	$248.10
Purchase #4	$168.88	4.105%	$175.8125	$175.81	$175.80	$175.80
Purchase #5	$87.38	4.498%	$91.3104	$91.31	$91.30	$91.30
Purchase #6	$200.87	10.321%	$221.6018	$221.60	$221.60	$221.60
Purchase #7	$65.53	6.686%	$69.9113	$69.91	$69.90	$69.90
7 purchase totals =	$1,054.26		$1,145.7804	$1,145.78	$1,145.75	$1,145.70