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	$75.46	13.109%	$85.3521	$85.35	$85.35	$85.40
Purchase #2	$205.71	3.651%	$213.2205	$213.22	$213.20	$213.20
Purchase #3	$221.28	10.401%	$244.2953	$244.30	$244.30	$244.30
Purchase #4	$134.92	9.626%	$147.9074	$147.91	$147.90	$147.90
Purchase #5	$72.34	12.751%	$81.5641	$81.56	$81.55	$81.60
Purchase #6	$93.83	7.826%	$101.1731	$101.17	$101.15	$101.20
Purchase #7	$119.35	9.266%	$130.409	$130.41	$130.40	$130.40
7 purchase totals =	$922.89		$1,003.9215	$1,003.92	$1,003.85	$1,004.00