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	$150.44	12.454%	$169.1758	$169.18	$169.20	$169.20
Purchase #2	$238.57	7.673%	$256.8755	$256.88	$256.90	$256.90
Purchase #3	$195.43	4.675%	$204.5664	$204.57	$204.55	$204.60
Purchase #4	$112.48	9.661%	$123.3467	$123.35	$123.35	$123.30
Purchase #5	$87.45	4.442%	$91.3345	$91.33	$91.35	$91.30
Purchase #6	$87.85	13.416%	$99.636	$99.64	$99.65	$99.60
Purchase #7	$68.53	13.514%	$77.7911	$77.79	$77.80	$77.80
7 purchase totals =	$940.75		$1,022.7260	$1,022.74	$1,022.80	$1,022.70