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	$180.89	5.525%	$190.8842	$190.88	$190.90	$190.90
Purchase #2	$78.41	5.492%	$82.7163	$82.72	$82.70	$82.70
Purchase #3	$177.91	11.726%	$198.7717	$198.77	$198.75	$198.80
Purchase #4	$48.85	13.424%	$55.4076	$55.41	$55.40	$55.40
Purchase #5	$32.68	4.438%	$34.1303	$34.13	$34.15	$34.10
Purchase #6	$79.92	12.438%	$89.8604	$89.86	$89.85	$89.90
Purchase #7	$57.52	9.277%	$62.8561	$62.86	$62.85	$62.90
7 purchase totals =	$656.18		$714.6266	$714.63	$714.60	$714.70