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	$149.67	12.282%	$168.0525	$168.05	$168.05	$168.10
Purchase #2	$54.31	4.231%	$56.6079	$56.61	$56.60	$56.60
Purchase #3	$154.85	10.569%	$171.2161	$171.22	$171.20	$171.20
Purchase #4	$163.36	11.167%	$181.6024	$181.60	$181.60	$181.60
Purchase #5	$234.52	7.285%	$251.6048	$251.60	$251.60	$251.60
Purchase #6	$179.90	3.141%	$185.5507	$185.55	$185.55	$185.60
Purchase #7	$114.76	10.708%	$127.0485	$127.05	$127.05	$127.00
7 purchase totals =	$1,051.37		$1,141.6829	$1,141.68	$1,141.65	$1,141.70