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	$215.55	12.830%	$243.2051	$243.21	$243.20	$243.20
Purchase #2	$159.54	7.473%	$171.4624	$171.46	$171.45	$171.50
Purchase #3	$110.93	3.613%	$114.9379	$114.94	$114.95	$114.90
Purchase #4	$72.94	8.191%	$78.9145	$78.91	$78.90	$78.90
Purchase #5	$208.82	11.305%	$232.4271	$232.43	$232.45	$232.40
Purchase #6	$169.50	8.295%	$183.56	$183.56	$183.55	$183.60
Purchase #7	$162.91	5.674%	$172.1535	$172.15	$172.15	$172.20
7 purchase totals =	$1,100.19		$1,196.6605	$1,196.66	$1,196.65	$1,196.70