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	$174.49	6.754%	$186.2751	$186.28	$186.30	$186.30
Purchase #2	$82.82	11.494%	$92.3393	$92.34	$92.35	$92.30
Purchase #3	$153.31	3.528%	$158.7188	$158.72	$158.70	$158.70
Purchase #4	$245.80	10.382%	$271.319	$271.32	$271.30	$271.30
Purchase #5	$171.85	4.338%	$179.3049	$179.30	$179.30	$179.30
Purchase #6	$218.60	4.530%	$228.5026	$228.50	$228.50	$228.50
Purchase #7	$196.84	4.780%	$206.249	$206.25	$206.25	$206.20
7 purchase totals =	$1,243.71		$1,322.7087	$1,322.71	$1,322.70	$1,322.60