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	$226.32	4.431%	$236.3482	$236.35	$236.35	$236.30
Purchase #2	$228.57	9.674%	$250.6819	$250.68	$250.70	$250.70
Purchase #3	$38.52	6.325%	$40.9564	$40.96	$40.95	$41.00
Purchase #4	$159.65	9.730%	$175.1839	$175.18	$175.20	$175.20
Purchase #5	$47.83	7.716%	$51.5206	$51.52	$51.50	$51.50
Purchase #6	$210.57	5.597%	$222.3556	$222.36	$222.35	$222.40
Purchase #7	$85.87	3.718%	$89.0626	$89.06	$89.05	$89.10
7 purchase totals =	$997.33		$1,066.1092	$1,066.11	$1,066.10	$1,066.20