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	$100.27	5.321%	$105.6054	$105.61	$105.60	$105.60
Purchase #2	$37.76	8.781%	$41.0757	$41.08	$41.10	$41.10
Purchase #3	$147.98	8.676%	$160.8187	$160.82	$160.80	$160.80
Purchase #4	$111.90	3.498%	$115.8143	$115.81	$115.80	$115.80
Purchase #5	$232.37	7.840%	$250.5878	$250.59	$250.60	$250.60
Purchase #6	$18.93	6.678%	$20.1941	$20.19	$20.20	$20.20
Purchase #7	$54.94	8.218%	$59.455	$59.46	$59.45	$59.50
7 purchase totals =	$704.15		$753.5510	$753.56	$753.55	$753.60