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	$243.70	4.280%	$254.1304	$254.13	$254.15	$254.10
Purchase #2	$155.89	11.215%	$173.3731	$173.37	$173.35	$173.40
Purchase #3	$249.65	5.284%	$262.8415	$262.84	$262.85	$262.80
Purchase #4	$125.85	4.613%	$131.6555	$131.66	$131.65	$131.70
Purchase #5	$50.76	6.144%	$53.8787	$53.88	$53.90	$53.90
Purchase #6	$148.63	4.612%	$155.4848	$155.48	$155.50	$155.50
Purchase #7	$130.62	9.443%	$142.9544	$142.95	$142.95	$143.00
7 purchase totals =	$1,105.10		$1,174.3184	$1,174.31	$1,174.35	$1,174.40