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	$17.72	7.524%	$19.0533	$19.05	$19.05	$19.10
Purchase #2	$164.56	10.356%	$181.6018	$181.60	$181.60	$181.60
Purchase #3	$118.36	13.666%	$134.5351	$134.54	$134.55	$134.50
Purchase #4	$30.49	8.637%	$33.1234	$33.12	$33.10	$33.10
Purchase #5	$122.60	7.297%	$131.5461	$131.55	$131.55	$131.50
Purchase #6	$179.28	9.829%	$196.9014	$196.90	$196.90	$196.90
Purchase #7	$6.56	5.573%	$6.9256	$6.93	$6.95	$6.90
7 purchase totals =	$639.57		$703.6867	$703.69	$703.70	$703.60