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	$69.43	11.821%	$77.6373	$77.64	$77.65	$77.60
Purchase #2	$19.79	7.438%	$21.262	$21.26	$21.25	$21.30
Purchase #3	$57.37	8.127%	$62.0325	$62.03	$62.05	$62.00
Purchase #4	$33.39	11.135%	$37.108	$37.11	$37.10	$37.10
Purchase #5	$229.53	11.230%	$255.3062	$255.31	$255.30	$255.30
Purchase #6	$110.52	7.481%	$118.788	$118.79	$118.80	$118.80
Purchase #7	$114.31	12.345%	$128.4216	$128.42	$128.40	$128.40
7 purchase totals =	$634.34		$700.5556	$700.56	$700.55	$700.50