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	$171.27	11.816%	$191.5073	$191.51	$191.50	$191.50
Purchase #2	$27.62	4.389%	$28.8322	$28.83	$28.85	$28.80
Purchase #3	$45.58	7.715%	$49.0965	$49.10	$49.10	$49.10
Purchase #4	$190.36	11.250%	$211.7755	$211.78	$211.80	$211.80
Purchase #5	$188.64	12.860%	$212.8991	$212.90	$212.90	$212.90
Purchase #6	$181.59	13.136%	$205.4437	$205.44	$205.45	$205.40
Purchase #7	$187.68	13.153%	$212.3656	$212.37	$212.35	$212.40
7 purchase totals =	$992.74		$1,111.9199	$1,111.93	$1,111.95	$1,111.90