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	$86.48	11.273%	$96.2289	$96.23	$96.25	$96.20
Purchase #2	$60.33	12.162%	$67.6673	$67.67	$67.65	$67.70
Purchase #3	$72.73	7.367%	$78.088	$78.09	$78.10	$78.10
Purchase #4	$49.43	4.223%	$51.5174	$51.52	$51.50	$51.50
Purchase #5	$119.53	11.312%	$133.0512	$133.05	$133.05	$133.10
Purchase #6	$220.57	11.242%	$245.3665	$245.37	$245.35	$245.40
Purchase #7	$124.35	9.698%	$136.4095	$136.41	$136.40	$136.40
7 purchase totals =	$733.42		$808.3288	$808.34	$808.30	$808.40