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	$203.59	3.515%	$210.7462	$210.75	$210.75	$210.70
Purchase #2	$32.55	8.431%	$35.2943	$35.29	$35.30	$35.30
Purchase #3	$75.45	9.548%	$82.654	$82.65	$82.65	$82.70
Purchase #4	$176.90	5.576%	$186.7639	$186.76	$186.75	$186.80
Purchase #5	$57.45	3.740%	$59.5986	$59.60	$59.60	$59.60
Purchase #6	$248.61	8.647%	$270.1073	$270.11	$270.10	$270.10
Purchase #7	$19.39	12.279%	$21.7709	$21.77	$21.75	$21.80
7 purchase totals =	$813.94		$866.9352	$866.93	$866.90	$867.00