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	$169.94	13.336%	$192.6032	$192.60	$192.60	$192.60
Purchase #2	$145.97	4.634%	$152.7342	$152.73	$152.75	$152.70
Purchase #3	$59.65	12.404%	$67.049	$67.05	$67.05	$67.00
Purchase #4	$196.36	10.149%	$216.2886	$216.29	$216.30	$216.30
Purchase #5	$106.91	4.537%	$111.7605	$111.76	$111.75	$111.80
Purchase #6	$167.41	11.518%	$186.6923	$186.69	$186.70	$186.70
Purchase #7	$137.98	12.165%	$154.7653	$154.77	$154.75	$154.80
7 purchase totals =	$984.22		$1,081.8931	$1,081.89	$1,081.90	$1,081.90