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	$69.28	13.830%	$78.8614	$78.86	$78.85	$78.90
Purchase #2	$171.84	13.396%	$194.8597	$194.86	$194.85	$194.90
Purchase #3	$37.36	9.533%	$40.9215	$40.92	$40.90	$40.90
Purchase #4	$11.41	6.408%	$12.1412	$12.14	$12.15	$12.10
Purchase #5	$27.36	3.843%	$28.4114	$28.41	$28.40	$28.40
Purchase #6	$99.96	5.799%	$105.7567	$105.76	$105.75	$105.80
Purchase #7	$62.50	5.781%	$66.1131	$66.11	$66.10	$66.10
7 purchase totals =	$479.71		$527.0650	$527.06	$527.00	$527.10