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	$128.65	10.585%	$142.2676	$142.27	$142.25	$142.30
Purchase #2	$168.31	3.315%	$173.8895	$173.89	$173.90	$173.90
Purchase #3	$25.54	11.874%	$28.5726	$28.57	$28.55	$28.60
Purchase #4	$16.72	7.870%	$18.0359	$18.04	$18.05	$18.00
Purchase #5	$58.49	10.738%	$64.7707	$64.77	$64.75	$64.80
Purchase #6	$221.48	9.331%	$242.1463	$242.15	$242.15	$242.10
Purchase #7	$248.69	7.139%	$266.444	$266.44	$266.45	$266.40
7 purchase totals =	$867.88		$936.1266	$936.13	$936.10	$936.10