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	$150.96	10.135%	$166.2598	$166.26	$166.25	$166.30
Purchase #2	$221.70	12.541%	$249.5034	$249.50	$249.50	$249.50
Purchase #3	$98.27	6.428%	$104.5868	$104.59	$104.60	$104.60
Purchase #4	$39.35	6.814%	$42.0313	$42.03	$42.05	$42.00
Purchase #5	$197.90	9.219%	$216.1444	$216.14	$216.15	$216.10
Purchase #6	$94.93	10.360%	$104.7647	$104.76	$104.75	$104.80
Purchase #7	$168.59	4.865%	$176.7919	$176.79	$176.80	$176.80
7 purchase totals =	$971.70		$1,060.0823	$1,060.07	$1,060.10	$1,060.10