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	$90.95	13.776%	$103.4793	$103.48	$103.50	$103.50
Purchase #2	$166.36	9.286%	$181.8082	$181.81	$181.80	$181.80
Purchase #3	$185.33	8.216%	$200.5567	$200.56	$200.55	$200.60
Purchase #4	$175.27	6.586%	$186.8133	$186.81	$186.80	$186.80
Purchase #5	$39.28	8.246%	$42.519	$42.52	$42.50	$42.50
Purchase #6	$211.40	8.558%	$229.4916	$229.49	$229.50	$229.50
Purchase #7	$22.33	5.501%	$23.5584	$23.56	$23.55	$23.60
7 purchase totals =	$890.92		$968.2265	$968.23	$968.20	$968.30