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	$130.42	3.195%	$134.5869	$134.59	$134.60	$134.60
Purchase #2	$182.96	10.194%	$201.6109	$201.61	$201.60	$201.60
Purchase #3	$82.48	10.298%	$90.9738	$90.97	$90.95	$91.00
Purchase #4	$79.73	12.519%	$89.7114	$89.71	$89.70	$89.70
Purchase #5	$31.38	7.263%	$33.6591	$33.66	$33.65	$33.70
Purchase #6	$250.47	8.316%	$271.2991	$271.30	$271.30	$271.30
Purchase #7	$250.27	9.305%	$273.5576	$273.56	$273.55	$273.60
7 purchase totals =	$1,007.71		$1,095.3988	$1,095.40	$1,095.35	$1,095.50