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	$198.97	13.318%	$225.4688	$225.47	$225.45	$225.50
Purchase #2	$222.52	8.264%	$240.9091	$240.91	$240.90	$240.90
Purchase #3	$223.47	7.779%	$240.8537	$240.85	$240.85	$240.90
Purchase #4	$133.51	7.150%	$143.056	$143.06	$143.05	$143.10
Purchase #5	$98.41	4.416%	$102.7558	$102.76	$102.75	$102.80
Purchase #6	$85.94	8.807%	$93.5087	$93.51	$93.50	$93.50
Purchase #7	$171.51	5.760%	$181.389	$181.39	$181.40	$181.40
7 purchase totals =	$1,134.33		$1,227.9411	$1,227.95	$1,227.90	$1,228.10