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	$106.79	9.814%	$117.2704	$117.27	$117.25	$117.30
Purchase #2	$34.28	12.575%	$38.5907	$38.59	$38.60	$38.60
Purchase #3	$142.54	11.159%	$158.446	$158.45	$158.45	$158.40
Purchase #4	$247.67	6.615%	$264.0534	$264.05	$264.05	$264.10
Purchase #5	$202.92	11.575%	$226.408	$226.41	$226.40	$226.40
Purchase #6	$39.95	6.758%	$42.6498	$42.65	$42.65	$42.60
Purchase #7	$89.72	13.196%	$101.5595	$101.56	$101.55	$101.60
7 purchase totals =	$863.87		$948.9778	$948.98	$948.95	$949.00