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	$249.32	7.617%	$268.3107	$268.31	$268.30	$268.30
Purchase #2	$32.29	9.839%	$35.467	$35.47	$35.45	$35.50
Purchase #3	$13.63	7.187%	$14.6096	$14.61	$14.60	$14.60
Purchase #4	$106.33	3.586%	$110.143	$110.14	$110.15	$110.10
Purchase #5	$106.40	11.425%	$118.5562	$118.56	$118.55	$118.60
Purchase #6	$45.86	12.134%	$51.4247	$51.42	$51.40	$51.40
Purchase #7	$160.45	3.106%	$165.4336	$165.43	$165.45	$165.40
7 purchase totals =	$714.28		$763.9448	$763.94	$763.90	$763.90