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	$174.63	4.645%	$182.7416	$182.74	$182.75	$182.70
Purchase #2	$249.28	10.469%	$275.3771	$275.38	$275.40	$275.40
Purchase #3	$50.53	8.630%	$54.8907	$54.89	$54.90	$54.90
Purchase #4	$241.39	5.156%	$253.8361	$253.84	$253.85	$253.80
Purchase #5	$50.82	13.310%	$57.5841	$57.58	$57.60	$57.60
Purchase #6	$210.77	3.479%	$218.1027	$218.10	$218.10	$218.10
Purchase #7	$13.90	10.157%	$15.3118	$15.31	$15.30	$15.30
7 purchase totals =	$991.32		$1,057.8441	$1,057.84	$1,057.90	$1,057.80