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	$93.26	3.244%	$96.2854	$96.29	$96.30	$96.30
Purchase #2	$104.48	9.853%	$114.7744	$114.77	$114.75	$114.80
Purchase #3	$88.52	4.393%	$92.4087	$92.41	$92.40	$92.40
Purchase #4	$166.39	11.330%	$185.242	$185.24	$185.25	$185.20
Purchase #5	$190.75	11.797%	$213.2528	$213.25	$213.25	$213.30
Purchase #6	$156.35	6.102%	$165.8905	$165.89	$165.90	$165.90
Purchase #7	$218.80	12.152%	$245.3886	$245.39	$245.40	$245.40
7 purchase totals =	$1,018.55		$1,113.2424	$1,113.24	$1,113.25	$1,113.30