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	$39.81	11.653%	$44.4491	$44.45	$44.45	$44.40
Purchase #2	$77.98	6.107%	$82.7422	$82.74	$82.75	$82.70
Purchase #3	$54.47	9.462%	$59.624	$59.62	$59.60	$59.60
Purchase #4	$71.64	8.807%	$77.9493	$77.95	$77.95	$77.90
Purchase #5	$28.76	9.867%	$31.5977	$31.60	$31.60	$31.60
Purchase #6	$181.66	4.320%	$189.5077	$189.51	$189.50	$189.50
Purchase #7	$67.89	13.604%	$77.1258	$77.13	$77.15	$77.10
7 purchase totals =	$522.21		$562.9958	$563.00	$563.00	$562.80