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	$63.85	5.170%	$67.151	$67.15	$67.15	$67.20
Purchase #2	$97.90	11.391%	$109.0518	$109.05	$109.05	$109.10
Purchase #3	$248.31	8.595%	$269.6522	$269.65	$269.65	$269.70
Purchase #4	$96.55	3.709%	$100.131	$100.13	$100.15	$100.10
Purchase #5	$141.86	10.107%	$156.1978	$156.20	$156.20	$156.20
Purchase #6	$30.79	3.639%	$31.9104	$31.91	$31.90	$31.90
Purchase #7	$200.51	9.802%	$220.164	$220.16	$220.15	$220.20
7 purchase totals =	$879.77		$954.2582	$954.25	$954.25	$954.40