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	$105.32	4.289%	$109.8372	$109.84	$109.85	$109.80
Purchase #2	$64.86	10.134%	$71.4329	$71.43	$71.45	$71.40
Purchase #3	$236.91	5.749%	$250.53	$250.53	$250.55	$250.50
Purchase #4	$182.77	13.657%	$207.7309	$207.73	$207.75	$207.70
Purchase #5	$199.78	6.463%	$212.6918	$212.69	$212.70	$212.70
Purchase #6	$88.62	12.480%	$99.6798	$99.68	$99.70	$99.70
Purchase #7	$54.43	5.201%	$57.2609	$57.26	$57.25	$57.30
7 purchase totals =	$932.69		$1,009.1635	$1,009.16	$1,009.25	$1,009.10