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	$193.60	10.825%	$214.5572	$214.56	$214.55	$214.60
Purchase #2	$21.82	3.191%	$22.5163	$22.52	$22.50	$22.50
Purchase #3	$39.46	6.839%	$42.1587	$42.16	$42.15	$42.20
Purchase #4	$170.92	12.816%	$192.8251	$192.83	$192.85	$192.80
Purchase #5	$80.33	7.718%	$86.5299	$86.53	$86.55	$86.50
Purchase #6	$69.45	12.394%	$78.0576	$78.06	$78.05	$78.10
Purchase #7	$12.62	10.211%	$13.9086	$13.91	$13.90	$13.90
7 purchase totals =	$588.20		$650.5534	$650.57	$650.55	$650.60