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	$228.45	7.510%	$245.6066	$245.61	$245.60	$245.60
Purchase #2	$208.33	3.832%	$216.3132	$216.31	$216.30	$216.30
Purchase #3	$147.82	7.558%	$158.9922	$158.99	$159.00	$159.00
Purchase #4	$169.96	11.373%	$189.2896	$189.29	$189.30	$189.30
Purchase #5	$64.34	11.109%	$71.4875	$71.49	$71.50	$71.50
Purchase #6	$146.71	3.868%	$152.3847	$152.38	$152.40	$152.40
Purchase #7	$110.73	12.745%	$124.8425	$124.84	$124.85	$124.80
7 purchase totals =	$1,076.34		$1,158.9163	$1,158.91	$1,158.95	$1,158.90