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	$242.87	4.360%	$253.4591	$253.46	$253.45	$253.50
Purchase #2	$199.31	8.258%	$215.769	$215.77	$215.75	$215.80
Purchase #3	$37.60	13.124%	$42.5346	$42.53	$42.55	$42.50
Purchase #4	$64.82	12.398%	$72.8564	$72.86	$72.85	$72.90
Purchase #5	$189.77	11.378%	$211.362	$211.36	$211.35	$211.40
Purchase #6	$130.34	6.280%	$138.5254	$138.53	$138.55	$138.50
Purchase #7	$9.54	4.158%	$9.9367	$9.94	$9.95	$9.90
7 purchase totals =	$874.25		$944.4432	$944.45	$944.45	$944.50