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	$126.46	4.150%	$131.7081	$131.71	$131.70	$131.70
Purchase #2	$170.36	10.398%	$188.074	$188.07	$188.05	$188.10
Purchase #3	$23.69	12.823%	$26.7278	$26.73	$26.75	$26.70
Purchase #4	$248.42	6.113%	$263.6059	$263.61	$263.60	$263.60
Purchase #5	$123.51	6.128%	$131.0787	$131.08	$131.10	$131.10
Purchase #6	$90.25	6.517%	$96.1316	$96.13	$96.15	$96.10
Purchase #7	$164.70	6.342%	$175.1453	$175.15	$175.15	$175.10
7 purchase totals =	$947.39		$1,012.4714	$1,012.48	$1,012.50	$1,012.40