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	$198.99	4.197%	$207.3416	$207.34	$207.35	$207.30
Purchase #2	$96.60	13.370%	$109.5154	$109.52	$109.50	$109.50
Purchase #3	$167.67	13.562%	$190.4094	$190.41	$190.40	$190.40
Purchase #4	$130.85	4.406%	$136.6153	$136.62	$136.60	$136.60
Purchase #5	$113.33	5.716%	$119.8079	$119.81	$119.80	$119.80
Purchase #6	$148.37	8.231%	$160.5823	$160.58	$160.60	$160.60
Purchase #7	$86.59	5.304%	$91.1827	$91.18	$91.20	$91.20
7 purchase totals =	$942.40		$1,015.4546	$1,015.46	$1,015.45	$1,015.40