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	$158.70	13.540%	$180.188	$180.19	$180.20	$180.20
Purchase #2	$46.70	7.470%	$50.1885	$50.19	$50.20	$50.20
Purchase #3	$49.61	9.582%	$54.3636	$54.36	$54.35	$54.40
Purchase #4	$86.66	4.391%	$90.4652	$90.47	$90.45	$90.50
Purchase #5	$46.64	11.375%	$51.9453	$51.95	$51.95	$51.90
Purchase #6	$39.37	8.790%	$42.8306	$42.83	$42.85	$42.80
Purchase #7	$61.37	9.261%	$67.0535	$67.05	$67.05	$67.10
7 purchase totals =	$489.05		$537.0347	$537.04	$537.05	$537.10