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	$167.77	9.869%	$184.3272	$184.33	$184.35	$184.30
Purchase #2	$91.85	13.742%	$104.472	$104.47	$104.45	$104.50
Purchase #3	$161.86	10.391%	$178.6789	$178.68	$178.70	$178.70
Purchase #4	$220.45	12.543%	$248.101	$248.10	$248.10	$248.10
Purchase #5	$73.55	12.156%	$82.4907	$82.49	$82.50	$82.50
Purchase #6	$53.94	4.421%	$56.3247	$56.32	$56.30	$56.30
Purchase #7	$103.77	7.819%	$111.8838	$111.88	$111.90	$111.90
7 purchase totals =	$873.19		$966.2783	$966.27	$966.30	$966.30