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	$162.28	13.417%	$184.0531	$184.05	$184.05	$184.10
Purchase #2	$6.34	13.396%	$7.1893	$7.19	$7.20	$7.20
Purchase #3	$128.30	11.320%	$142.8236	$142.82	$142.80	$142.80
Purchase #4	$52.46	3.466%	$54.2783	$54.28	$54.30	$54.30
Purchase #5	$244.64	12.612%	$275.494	$275.49	$275.50	$275.50
Purchase #6	$28.39	11.811%	$31.7431	$31.74	$31.75	$31.70
Purchase #7	$163.44	13.502%	$185.5077	$185.51	$185.50	$185.50
7 purchase totals =	$785.85		$881.0891	$881.08	$881.10	$881.10