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	$173.48	9.855%	$190.5765	$190.58	$190.60	$190.60
Purchase #2	$172.69	6.787%	$184.4105	$184.41	$184.40	$184.40
Purchase #3	$250.53	9.728%	$274.9016	$274.90	$274.90	$274.90
Purchase #4	$127.56	11.414%	$142.1197	$142.12	$142.10	$142.10
Purchase #5	$65.49	3.280%	$67.6381	$67.64	$67.65	$67.60
Purchase #6	$72.52	4.773%	$75.9814	$75.98	$76.00	$76.00
Purchase #7	$245.84	3.414%	$254.233	$254.23	$254.25	$254.20
7 purchase totals =	$1,108.11		$1,189.8608	$1,189.86	$1,189.90	$1,189.80