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	$91.56	11.766%	$102.3329	$102.33	$102.35	$102.30
Purchase #2	$67.44	7.356%	$72.4009	$72.40	$72.40	$72.40
Purchase #3	$158.39	9.356%	$173.209	$173.21	$173.20	$173.20
Purchase #4	$114.51	11.855%	$128.0852	$128.09	$128.10	$128.10
Purchase #5	$49.31	12.102%	$55.2775	$55.28	$55.30	$55.30
Purchase #6	$65.44	12.801%	$73.817	$73.82	$73.80	$73.80
Purchase #7	$105.38	12.859%	$118.9308	$118.93	$118.95	$118.90
7 purchase totals =	$652.03		$724.0533	$724.06	$724.10	$724.00