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	$89.81	9.203%	$98.0752	$98.08	$98.10	$98.10
Purchase #2	$223.78	9.429%	$244.8802	$244.88	$244.90	$244.90
Purchase #3	$42.75	5.143%	$44.9486	$44.95	$44.95	$44.90
Purchase #4	$39.73	7.569%	$42.7372	$42.74	$42.75	$42.70
Purchase #5	$5.81	5.338%	$6.1201	$6.12	$6.10	$6.10
Purchase #6	$181.62	8.114%	$196.3566	$196.36	$196.35	$196.40
Purchase #7	$140.78	6.644%	$150.1334	$150.13	$150.15	$150.10
7 purchase totals =	$724.28		$783.2513	$783.26	$783.30	$783.20