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	$65.87	10.585%	$72.8423	$72.84	$72.85	$72.80
Purchase #2	$101.96	3.467%	$105.495	$105.50	$105.50	$105.50
Purchase #3	$88.86	9.126%	$96.9694	$96.97	$96.95	$97.00
Purchase #4	$64.91	11.403%	$72.3117	$72.31	$72.30	$72.30
Purchase #5	$91.68	13.171%	$103.7552	$103.76	$103.75	$103.80
Purchase #6	$150.40	6.578%	$160.2933	$160.29	$160.30	$160.30
Purchase #7	$35.72	10.202%	$39.3642	$39.36	$39.35	$39.40
7 purchase totals =	$599.40		$651.0311	$651.03	$651.00	$651.10