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	$161.56	11.684%	$180.4367	$180.44	$180.45	$180.40
Purchase #2	$173.31	3.365%	$179.1419	$179.14	$179.15	$179.10
Purchase #3	$83.90	3.326%	$86.6905	$86.69	$86.70	$86.70
Purchase #4	$184.36	6.534%	$196.4061	$196.41	$196.40	$196.40
Purchase #5	$64.49	8.371%	$69.8885	$69.89	$69.90	$69.90
Purchase #6	$80.36	12.855%	$90.6903	$90.69	$90.70	$90.70
Purchase #7	$48.48	13.655%	$55.0999	$55.10	$55.10	$55.10
7 purchase totals =	$796.46		$858.3539	$858.36	$858.40	$858.30