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	$137.58	7.142%	$147.406	$147.41	$147.40	$147.40
Purchase #2	$170.97	5.140%	$179.7579	$179.76	$179.75	$179.80
Purchase #3	$144.32	8.344%	$156.3621	$156.36	$156.35	$156.40
Purchase #4	$136.94	4.144%	$142.6148	$142.61	$142.60	$142.60
Purchase #5	$224.52	8.449%	$243.4897	$243.49	$243.50	$243.50
Purchase #6	$209.44	6.670%	$223.4096	$223.41	$223.40	$223.40
Purchase #7	$164.32	4.587%	$171.8574	$171.86	$171.85	$171.90
7 purchase totals =	$1,188.09		$1,264.8975	$1,264.90	$1,264.85	$1,265.00