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	$87.43	12.785%	$98.6079	$98.61	$98.60	$98.60
Purchase #2	$68.71	3.178%	$70.8936	$70.89	$70.90	$70.90
Purchase #3	$122.61	6.162%	$130.1652	$130.17	$130.15	$130.20
Purchase #4	$62.46	4.194%	$65.0796	$65.08	$65.10	$65.10
Purchase #5	$79.39	3.647%	$82.2854	$82.29	$82.30	$82.30
Purchase #6	$165.51	3.555%	$171.3939	$171.39	$171.40	$171.40
Purchase #7	$210.63	3.793%	$218.6192	$218.62	$218.60	$218.60
7 purchase totals =	$796.74		$837.0448	$837.05	$837.05	$837.10