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	$111.57	6.383%	$118.6915	$118.69	$118.70	$118.70
Purchase #2	$105.61	6.522%	$112.4979	$112.50	$112.50	$112.50
Purchase #3	$166.66	10.439%	$184.0576	$184.06	$184.05	$184.10
Purchase #4	$14.39	6.413%	$15.3128	$15.31	$15.30	$15.30
Purchase #5	$244.48	6.310%	$259.9067	$259.91	$259.90	$259.90
Purchase #6	$127.98	7.611%	$137.7206	$137.72	$137.70	$137.70
Purchase #7	$166.84	13.123%	$188.7344	$188.73	$188.75	$188.70
7 purchase totals =	$937.53		$1,016.9215	$1,016.92	$1,016.90	$1,016.90