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	$59.83	3.803%	$62.1053	$62.11	$62.10	$62.10
Purchase #2	$169.69	10.497%	$187.5024	$187.50	$187.50	$187.50
Purchase #3	$235.29	6.382%	$250.3062	$250.31	$250.30	$250.30
Purchase #4	$40.55	10.556%	$44.8305	$44.83	$44.85	$44.80
Purchase #5	$83.42	10.357%	$92.0598	$92.06	$92.05	$92.10
Purchase #6	$220.35	11.356%	$245.3729	$245.37	$245.35	$245.40
Purchase #7	$150.71	12.227%	$169.1373	$169.14	$169.15	$169.10
7 purchase totals =	$959.84		$1,051.3144	$1,051.32	$1,051.30	$1,051.30