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	$64.86	11.459%	$72.2923	$72.29	$72.30	$72.30
Purchase #2	$12.51	7.222%	$13.4135	$13.41	$13.40	$13.40
Purchase #3	$23.35	10.219%	$25.7361	$25.74	$25.75	$25.70
Purchase #4	$75.33	7.190%	$80.7462	$80.75	$80.75	$80.70
Purchase #5	$23.53	7.747%	$25.3529	$25.35	$25.35	$25.40
Purchase #6	$71.35	10.538%	$78.8689	$78.87	$78.85	$78.90
Purchase #7	$102.97	5.763%	$108.9042	$108.90	$108.90	$108.90
7 purchase totals =	$373.90		$405.3141	$405.31	$405.30	$405.30