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	$164.88	7.460%	$177.18	$177.18	$177.20	$177.20
Purchase #2	$151.94	12.613%	$171.1042	$171.10	$171.10	$171.10
Purchase #3	$55.32	7.412%	$59.4203	$59.42	$59.40	$59.40
Purchase #4	$38.96	4.708%	$40.7942	$40.79	$40.80	$40.80
Purchase #5	$150.65	11.497%	$167.9702	$167.97	$167.95	$168.00
Purchase #6	$114.82	7.591%	$123.536	$123.54	$123.55	$123.50
Purchase #7	$213.68	4.729%	$223.7849	$223.78	$223.80	$223.80
7 purchase totals =	$890.25		$963.7898	$963.78	$963.80	$963.80