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	$133.71	6.227%	$142.0361	$142.04	$142.05	$142.00
Purchase #2	$245.27	4.173%	$255.5051	$255.51	$255.50	$255.50
Purchase #3	$34.61	3.485%	$35.8162	$35.82	$35.80	$35.80
Purchase #4	$42.30	11.443%	$47.1404	$47.14	$47.15	$47.10
Purchase #5	$90.76	8.183%	$98.1869	$98.19	$98.20	$98.20
Purchase #6	$12.79	13.847%	$14.561	$14.56	$14.55	$14.60
Purchase #7	$78.72	6.340%	$83.7108	$83.71	$83.70	$83.70
7 purchase totals =	$638.16		$676.9565	$676.97	$676.95	$676.90