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	$179.50	5.363%	$189.1266	$189.13	$189.15	$189.10
Purchase #2	$199.27	6.568%	$212.3581	$212.36	$212.35	$212.40
Purchase #3	$213.45	4.872%	$223.8493	$223.85	$223.85	$223.80
Purchase #4	$69.29	3.504%	$71.7179	$71.72	$71.70	$71.70
Purchase #5	$183.50	3.798%	$190.4693	$190.47	$190.45	$190.50
Purchase #6	$233.32	12.577%	$262.6647	$262.66	$262.65	$262.70
Purchase #7	$68.88	7.155%	$73.8084	$73.81	$73.80	$73.80
7 purchase totals =	$1,147.21		$1,223.9943	$1,224.00	$1,223.95	$1,224.00