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	$118.31	5.287%	$124.565	$124.57	$124.55	$124.60
Purchase #2	$105.54	4.649%	$110.4466	$110.45	$110.45	$110.40
Purchase #3	$245.97	3.218%	$253.8853	$253.89	$253.90	$253.90
Purchase #4	$200.87	13.251%	$227.4873	$227.49	$227.50	$227.50
Purchase #5	$223.56	12.289%	$251.0333	$251.03	$251.05	$251.00
Purchase #6	$79.83	3.211%	$82.3933	$82.39	$82.40	$82.40
Purchase #7	$63.94	13.256%	$72.4159	$72.42	$72.40	$72.40
7 purchase totals =	$1,038.02		$1,122.2267	$1,122.24	$1,122.25	$1,122.20