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	$49.53	4.493%	$51.7554	$51.76	$51.75	$51.80
Purchase #2	$62.81	7.495%	$67.5176	$67.52	$67.50	$67.50
Purchase #3	$191.90	8.539%	$208.2863	$208.29	$208.30	$208.30
Purchase #4	$235.76	12.183%	$264.4826	$264.48	$264.50	$264.50
Purchase #5	$76.61	7.368%	$82.2546	$82.25	$82.25	$82.30
Purchase #6	$26.91	3.768%	$27.924	$27.92	$27.90	$27.90
Purchase #7	$93.43	13.284%	$105.8412	$105.84	$105.85	$105.80
7 purchase totals =	$736.95		$808.0617	$808.06	$808.05	$808.10