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	$79.30	5.249%	$83.4625	$83.46	$83.45	$83.50
Purchase #2	$31.27	5.768%	$33.0737	$33.07	$33.05	$33.10
Purchase #3	$54.90	12.325%	$61.6664	$61.67	$61.65	$61.70
Purchase #4	$35.33	11.172%	$39.2771	$39.28	$39.30	$39.30
Purchase #5	$156.78	3.852%	$162.8192	$162.82	$162.80	$162.80
Purchase #6	$85.78	13.248%	$97.1441	$97.14	$97.15	$97.10
Purchase #7	$191.34	10.759%	$211.9263	$211.93	$211.95	$211.90
7 purchase totals =	$634.70		$689.3693	$689.37	$689.35	$689.40