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	$156.62	11.425%	$174.5138	$174.51	$174.50	$174.50
Purchase #2	$137.68	3.640%	$142.6916	$142.69	$142.70	$142.70
Purchase #3	$190.79	13.241%	$216.0525	$216.05	$216.05	$216.10
Purchase #4	$211.77	4.791%	$221.9159	$221.92	$221.90	$221.90
Purchase #5	$34.82	9.562%	$38.1495	$38.15	$38.15	$38.10
Purchase #6	$198.82	12.328%	$223.3305	$223.33	$223.35	$223.30
Purchase #7	$38.87	12.405%	$43.6918	$43.69	$43.70	$43.70
7 purchase totals =	$969.37		$1,060.3456	$1,060.34	$1,060.35	$1,060.30