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	$184.46	3.601%	$191.1024	$191.10	$191.10	$191.10
Purchase #2	$114.30	5.190%	$120.2322	$120.23	$120.25	$120.20
Purchase #3	$140.33	13.218%	$158.8788	$158.88	$158.90	$158.90
Purchase #4	$55.83	7.277%	$59.8927	$59.89	$59.90	$59.90
Purchase #5	$208.99	11.867%	$233.7908	$233.79	$233.80	$233.80
Purchase #6	$147.45	4.799%	$154.5261	$154.53	$154.55	$154.50
Purchase #7	$140.64	11.796%	$157.2299	$157.23	$157.25	$157.20
7 purchase totals =	$992.00		$1,075.6529	$1,075.65	$1,075.75	$1,075.60