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	$223.65	9.755%	$245.4671	$245.47	$245.45	$245.50
Purchase #2	$173.90	3.849%	$180.5934	$180.59	$180.60	$180.60
Purchase #3	$147.41	8.290%	$159.6303	$159.63	$159.65	$159.60
Purchase #4	$156.85	10.199%	$172.8471	$172.85	$172.85	$172.80
Purchase #5	$7.54	10.196%	$8.3088	$8.31	$8.30	$8.30
Purchase #6	$42.72	9.285%	$46.6866	$46.69	$46.70	$46.70
Purchase #7	$220.76	4.760%	$231.2682	$231.27	$231.25	$231.30
7 purchase totals =	$972.83		$1,044.8015	$1,044.81	$1,044.80	$1,044.80