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	$85.26	13.526%	$96.7923	$96.79	$96.80	$96.80
Purchase #2	$212.56	4.133%	$221.3451	$221.35	$221.35	$221.30
Purchase #3	$35.34	10.280%	$38.973	$38.97	$38.95	$39.00
Purchase #4	$135.31	5.159%	$142.2906	$142.29	$142.30	$142.30
Purchase #5	$63.73	4.852%	$66.8222	$66.82	$66.80	$66.80
Purchase #6	$120.71	5.752%	$127.6532	$127.65	$127.65	$127.70
Purchase #7	$160.90	7.505%	$172.9755	$172.98	$173.00	$173.00
7 purchase totals =	$813.81		$866.8519	$866.85	$866.85	$866.90