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	$100.59	4.421%	$105.0371	$105.04	$105.05	$105.00
Purchase #2	$81.91	4.774%	$85.8204	$85.82	$85.80	$85.80
Purchase #3	$83.98	5.391%	$88.5074	$88.51	$88.50	$88.50
Purchase #4	$249.53	3.123%	$257.3228	$257.32	$257.30	$257.30
Purchase #5	$149.26	7.830%	$160.9471	$160.95	$160.95	$160.90
Purchase #6	$184.56	13.699%	$209.8429	$209.84	$209.85	$209.80
Purchase #7	$129.63	7.656%	$139.5545	$139.55	$139.55	$139.60
7 purchase totals =	$979.46		$1,047.0322	$1,047.03	$1,047.00	$1,046.90