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	$234.25	11.734%	$261.7369	$261.74	$261.75	$261.70
Purchase #2	$55.42	7.524%	$59.5898	$59.59	$59.60	$59.60
Purchase #3	$60.57	3.740%	$62.8353	$62.84	$62.85	$62.80
Purchase #4	$246.85	8.372%	$267.5163	$267.52	$267.50	$267.50
Purchase #5	$203.90	5.258%	$214.6211	$214.62	$214.60	$214.60
Purchase #6	$189.74	11.515%	$211.5886	$211.59	$211.60	$211.60
Purchase #7	$123.74	6.218%	$131.4342	$131.43	$131.45	$131.40
7 purchase totals =	$1,114.47		$1,209.3222	$1,209.33	$1,209.35	$1,209.20