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	$169.47	13.849%	$192.9399	$192.94	$192.95	$192.90
Purchase #2	$77.61	3.827%	$80.5801	$80.58	$80.60	$80.60
Purchase #3	$55.58	6.258%	$59.0582	$59.06	$59.05	$59.10
Purchase #4	$98.72	9.363%	$107.9632	$107.96	$107.95	$108.00
Purchase #5	$25.98	9.362%	$28.4122	$28.41	$28.40	$28.40
Purchase #6	$52.33	13.173%	$59.2234	$59.22	$59.20	$59.20
Purchase #7	$197.68	13.314%	$223.9991	$224.00	$224.00	$224.00
7 purchase totals =	$677.37		$752.1761	$752.17	$752.15	$752.20