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	$123.33	6.440%	$131.2725	$131.27	$131.25	$131.30
Purchase #2	$150.70	9.414%	$164.8869	$164.89	$164.90	$164.90
Purchase #3	$47.95	4.420%	$50.0694	$50.07	$50.05	$50.10
Purchase #4	$201.48	4.131%	$209.8031	$209.80	$209.80	$209.80
Purchase #5	$212.45	5.140%	$223.3699	$223.37	$223.35	$223.40
Purchase #6	$196.45	9.116%	$214.3584	$214.36	$214.35	$214.40
Purchase #7	$234.82	5.204%	$247.04	$247.04	$247.05	$247.00
7 purchase totals =	$1,167.18		$1,240.8002	$1,240.80	$1,240.75	$1,240.90