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	$62.39	7.835%	$67.2783	$67.28	$67.30	$67.30
Purchase #2	$45.55	13.769%	$51.8218	$51.82	$51.80	$51.80
Purchase #3	$174.61	3.102%	$180.0264	$180.03	$180.05	$180.00
Purchase #4	$107.37	7.425%	$115.3422	$115.34	$115.35	$115.30
Purchase #5	$125.93	4.511%	$131.6107	$131.61	$131.60	$131.60
Purchase #6	$200.47	11.519%	$223.5621	$223.56	$223.55	$223.60
Purchase #7	$76.51	3.620%	$79.2797	$79.28	$79.30	$79.30
7 purchase totals =	$792.83		$848.9212	$848.92	$848.95	$848.90