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	$102.82	9.546%	$112.6352	$112.64	$112.65	$112.60
Purchase #2	$223.73	13.766%	$254.5287	$254.53	$254.55	$254.50
Purchase #3	$75.70	12.753%	$85.354	$85.35	$85.35	$85.40
Purchase #4	$86.35	13.457%	$97.9701	$97.97	$97.95	$98.00
Purchase #5	$79.25	3.870%	$82.317	$82.32	$82.30	$82.30
Purchase #6	$88.82	10.493%	$98.1399	$98.14	$98.15	$98.10
Purchase #7	$48.79	10.613%	$53.9681	$53.97	$53.95	$54.00
7 purchase totals =	$705.46		$784.9130	$784.92	$784.90	$784.90