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	$91.37	11.481%	$101.8602	$101.86	$101.85	$101.90
Purchase #2	$69.47	9.268%	$75.9085	$75.91	$75.90	$75.90
Purchase #3	$98.46	5.435%	$103.8113	$103.81	$103.80	$103.80
Purchase #4	$201.49	3.796%	$209.1386	$209.14	$209.15	$209.10
Purchase #5	$123.59	3.120%	$127.446	$127.45	$127.45	$127.40
Purchase #6	$227.42	11.836%	$254.3374	$254.34	$254.35	$254.30
Purchase #7	$127.97	7.666%	$137.7802	$137.78	$137.80	$137.80
7 purchase totals =	$939.77		$1,010.2822	$1,010.29	$1,010.30	$1,010.20