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	$174.46	12.802%	$196.7944	$196.79	$196.80	$196.80
Purchase #2	$135.81	7.312%	$145.7404	$145.74	$145.75	$145.70
Purchase #3	$124.30	5.473%	$131.1029	$131.10	$131.10	$131.10
Purchase #4	$13.99	11.548%	$15.6056	$15.61	$15.60	$15.60
Purchase #5	$160.62	13.163%	$181.7624	$181.76	$181.75	$181.80
Purchase #6	$122.38	11.635%	$136.6189	$136.62	$136.60	$136.60
Purchase #7	$67.85	6.389%	$72.1849	$72.18	$72.20	$72.20
7 purchase totals =	$799.41		$879.8095	$879.80	$879.80	$879.80