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	$238.79	12.859%	$269.496	$269.50	$269.50	$269.50
Purchase #2	$193.56	9.808%	$212.5444	$212.54	$212.55	$212.50
Purchase #3	$158.28	8.635%	$171.9475	$171.95	$171.95	$171.90
Purchase #4	$243.31	12.401%	$273.4829	$273.48	$273.50	$273.50
Purchase #5	$229.52	9.131%	$250.4775	$250.48	$250.50	$250.50
Purchase #6	$134.62	9.873%	$147.911	$147.91	$147.90	$147.90
Purchase #7	$148.56	9.631%	$162.8678	$162.87	$162.85	$162.90
7 purchase totals =	$1,346.64		$1,488.7271	$1,488.73	$1,488.75	$1,488.70