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	$93.49	7.608%	$100.6027	$100.60	$100.60	$100.60
Purchase #2	$224.43	12.343%	$252.1314	$252.13	$252.15	$252.10
Purchase #3	$88.53	9.128%	$96.611	$96.61	$96.60	$96.60
Purchase #4	$250.30	7.764%	$269.7333	$269.73	$269.75	$269.70
Purchase #5	$56.90	9.470%	$62.2884	$62.29	$62.30	$62.30
Purchase #6	$136.39	11.106%	$151.5375	$151.54	$151.55	$151.50
Purchase #7	$74.68	4.698%	$78.1885	$78.19	$78.20	$78.20
7 purchase totals =	$924.72		$1,011.0928	$1,011.09	$1,011.15	$1,011.00