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	$69.56	4.767%	$72.8759	$72.88	$72.90	$72.90
Purchase #2	$83.42	13.460%	$94.6483	$94.65	$94.65	$94.60
Purchase #3	$205.25	3.718%	$212.8812	$212.88	$212.90	$212.90
Purchase #4	$122.49	6.438%	$130.3759	$130.38	$130.40	$130.40
Purchase #5	$170.46	5.642%	$180.0774	$180.08	$180.10	$180.10
Purchase #6	$55.61	6.391%	$59.164	$59.16	$59.15	$59.20
Purchase #7	$89.29	7.147%	$95.6716	$95.67	$95.65	$95.70
7 purchase totals =	$796.08		$845.6943	$845.70	$845.75	$845.80