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	$169.25	9.500%	$185.3288	$185.33	$185.35	$185.30
Purchase #2	$110.73	13.499%	$125.6774	$125.68	$125.70	$125.70
Purchase #3	$152.85	7.815%	$164.7952	$164.80	$164.80	$164.80
Purchase #4	$152.60	4.726%	$159.8119	$159.81	$159.80	$159.80
Purchase #5	$175.88	8.276%	$190.4358	$190.44	$190.45	$190.40
Purchase #6	$201.26	11.253%	$223.9078	$223.91	$223.90	$223.90
Purchase #7	$99.48	4.465%	$103.9218	$103.92	$103.90	$103.90
7 purchase totals =	$1,062.05		$1,153.8787	$1,153.89	$1,153.90	$1,153.80