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	$88.29	9.287%	$96.4895	$96.49	$96.50	$96.50
Purchase #2	$9.61	9.788%	$10.5506	$10.55	$10.55	$10.60
Purchase #3	$97.28	6.550%	$103.6518	$103.65	$103.65	$103.70
Purchase #4	$228.84	11.251%	$254.5868	$254.59	$254.60	$254.60
Purchase #5	$225.60	10.526%	$249.3467	$249.35	$249.35	$249.30
Purchase #6	$205.64	3.533%	$212.9053	$212.91	$212.90	$212.90
Purchase #7	$178.52	3.160%	$184.1612	$184.16	$184.15	$184.20
7 purchase totals =	$1,033.78		$1,111.6919	$1,111.70	$1,111.70	$1,111.80