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	$161.99	6.377%	$172.3201	$172.32	$172.30	$172.30
Purchase #2	$74.47	4.613%	$77.9053	$77.91	$77.90	$77.90
Purchase #3	$80.72	12.438%	$90.76	$90.76	$90.75	$90.80
Purchase #4	$213.31	12.790%	$240.5923	$240.59	$240.60	$240.60
Purchase #5	$197.64	5.788%	$209.0794	$209.08	$209.10	$209.10
Purchase #6	$94.50	10.685%	$104.5973	$104.60	$104.60	$104.60
Purchase #7	$158.48	6.799%	$169.2551	$169.26	$169.25	$169.30
7 purchase totals =	$981.11		$1,064.5095	$1,064.52	$1,064.50	$1,064.60