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	$136.86	10.282%	$150.9319	$150.93	$150.95	$150.90
Purchase #2	$130.52	8.808%	$142.0162	$142.02	$142.00	$142.00
Purchase #3	$126.82	12.351%	$142.4835	$142.48	$142.50	$142.50
Purchase #4	$67.29	3.114%	$69.3854	$69.39	$69.40	$69.40
Purchase #5	$112.92	9.398%	$123.5322	$123.53	$123.55	$123.50
Purchase #6	$110.50	3.325%	$114.1741	$114.17	$114.15	$114.20
Purchase #7	$47.84	6.144%	$50.7793	$50.78	$50.80	$50.80
7 purchase totals =	$732.75		$793.3026	$793.30	$793.35	$793.30