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	$166.64	11.567%	$185.9152	$185.92	$185.90	$185.90
Purchase #2	$228.95	5.501%	$241.5445	$241.54	$241.55	$241.50
Purchase #3	$167.75	11.690%	$187.36	$187.36	$187.35	$187.40
Purchase #4	$86.52	11.345%	$96.3357	$96.34	$96.35	$96.30
Purchase #5	$227.74	8.796%	$247.772	$247.77	$247.75	$247.80
Purchase #6	$52.78	4.767%	$55.296	$55.30	$55.30	$55.30
Purchase #7	$38.95	9.720%	$42.7359	$42.74	$42.75	$42.70
7 purchase totals =	$969.33		$1,056.9593	$1,056.97	$1,056.95	$1,056.90