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	$109.86	7.435%	$118.0281	$118.03	$118.05	$118.00
Purchase #2	$201.54	6.410%	$214.4587	$214.46	$214.45	$214.50
Purchase #3	$218.96	4.316%	$228.4103	$228.41	$228.40	$228.40
Purchase #4	$92.85	13.215%	$105.1201	$105.12	$105.10	$105.10
Purchase #5	$22.67	10.573%	$25.0669	$25.07	$25.05	$25.10
Purchase #6	$184.85	6.184%	$196.2811	$196.28	$196.30	$196.30
Purchase #7	$78.99	7.685%	$85.0604	$85.06	$85.05	$85.10
7 purchase totals =	$909.72		$972.4256	$972.43	$972.40	$972.50