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	$222.73	12.268%	$250.0545	$250.05	$250.05	$250.10
Purchase #2	$106.85	5.485%	$112.7107	$112.71	$112.70	$112.70
Purchase #3	$209.76	10.797%	$232.4078	$232.41	$232.40	$232.40
Purchase #4	$178.71	8.597%	$194.0737	$194.07	$194.05	$194.10
Purchase #5	$206.81	7.469%	$222.2566	$222.26	$222.25	$222.30
Purchase #6	$83.41	8.623%	$90.6024	$90.60	$90.60	$90.60
Purchase #7	$8.62	10.522%	$9.527	$9.53	$9.55	$9.50
7 purchase totals =	$1,016.89		$1,111.6327	$1,111.63	$1,111.60	$1,111.70