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	$6.82	10.598%	$7.5428	$7.54	$7.55	$7.50
Purchase #2	$118.54	3.559%	$122.7588	$122.76	$122.75	$122.80
Purchase #3	$182.33	7.552%	$196.0996	$196.10	$196.10	$196.10
Purchase #4	$154.87	13.872%	$176.3536	$176.35	$176.35	$176.40
Purchase #5	$79.72	8.471%	$86.4731	$86.47	$86.45	$86.50
Purchase #6	$99.72	3.357%	$103.0676	$103.07	$103.05	$103.10
Purchase #7	$89.65	3.477%	$92.7671	$92.77	$92.75	$92.80
7 purchase totals =	$731.65		$785.0626	$785.06	$785.00	$785.20