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	$119.61	6.849%	$127.8021	$127.80	$127.80	$127.80
Purchase #2	$116.45	7.586%	$125.2839	$125.28	$125.30	$125.30
Purchase #3	$28.46	9.810%	$31.2519	$31.25	$31.25	$31.30
Purchase #4	$156.32	8.506%	$169.6166	$169.62	$169.60	$169.60
Purchase #5	$147.32	3.358%	$152.267	$152.27	$152.25	$152.30
Purchase #6	$174.48	11.615%	$194.7459	$194.75	$194.75	$194.70
Purchase #7	$128.75	3.247%	$132.9305	$132.93	$132.95	$132.90
7 purchase totals =	$871.39		$933.8979	$933.90	$933.90	$933.90