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	$161.95	12.409%	$182.0464	$182.05	$182.05	$182.00
Purchase #2	$228.68	11.740%	$255.527	$255.53	$255.55	$255.50
Purchase #3	$39.27	9.110%	$42.8475	$42.85	$42.85	$42.80
Purchase #4	$54.32	7.645%	$58.4728	$58.47	$58.45	$58.50
Purchase #5	$243.39	9.865%	$267.4004	$267.40	$267.40	$267.40
Purchase #6	$80.41	9.865%	$88.3424	$88.34	$88.35	$88.30
Purchase #7	$217.51	7.333%	$233.46	$233.46	$233.45	$233.50
7 purchase totals =	$1,025.53		$1,128.0965	$1,128.10	$1,128.10	$1,128.00