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	$188.43	9.206%	$205.7769	$205.78	$205.80	$205.80
Purchase #2	$169.56	6.457%	$180.5085	$180.51	$180.50	$180.50
Purchase #3	$64.42	11.398%	$71.7626	$71.76	$71.75	$71.80
Purchase #4	$191.61	3.794%	$198.8797	$198.88	$198.90	$198.90
Purchase #5	$135.52	8.613%	$147.1923	$147.19	$147.20	$147.20
Purchase #6	$74.85	10.468%	$82.6853	$82.69	$82.70	$82.70
Purchase #7	$215.88	6.427%	$229.7546	$229.75	$229.75	$229.80
7 purchase totals =	$1,040.27		$1,116.5599	$1,116.56	$1,116.60	$1,116.70