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	$61.42	9.263%	$67.1093	$67.11	$67.10	$67.10
Purchase #2	$129.46	8.831%	$140.8926	$140.89	$140.90	$140.90
Purchase #3	$224.89	10.420%	$248.3235	$248.32	$248.30	$248.30
Purchase #4	$46.45	13.631%	$52.7816	$52.78	$52.80	$52.80
Purchase #5	$102.73	13.254%	$116.3458	$116.35	$116.35	$116.30
Purchase #6	$191.69	12.289%	$215.2468	$215.25	$215.25	$215.20
Purchase #7	$110.93	12.172%	$124.4324	$124.43	$124.45	$124.40
7 purchase totals =	$867.57		$965.1320	$965.13	$965.15	$965.00