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	$131.81	8.411%	$142.8965	$142.90	$142.90	$142.90
Purchase #2	$121.98	8.146%	$131.9165	$131.92	$131.90	$131.90
Purchase #3	$165.87	5.628%	$175.2052	$175.21	$175.20	$175.20
Purchase #4	$159.54	9.489%	$174.6788	$174.68	$174.70	$174.70
Purchase #5	$140.32	4.201%	$146.2148	$146.21	$146.20	$146.20
Purchase #6	$133.53	12.851%	$150.6899	$150.69	$150.70	$150.70
Purchase #7	$214.61	3.568%	$222.2673	$222.27	$222.25	$222.30
7 purchase totals =	$1,067.66		$1,143.8690	$1,143.88	$1,143.85	$1,143.90