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	$169.76	4.687%	$177.7167	$177.72	$177.70	$177.70
Purchase #2	$96.77	10.373%	$106.808	$106.81	$106.80	$106.80
Purchase #3	$57.92	7.178%	$62.0775	$62.08	$62.10	$62.10
Purchase #4	$232.81	9.483%	$254.8874	$254.89	$254.90	$254.90
Purchase #5	$247.32	10.848%	$274.1493	$274.15	$274.15	$274.10
Purchase #6	$84.59	6.250%	$89.8769	$89.88	$89.90	$89.90
Purchase #7	$94.74	6.595%	$100.9881	$100.99	$101.00	$101.00
7 purchase totals =	$983.91		$1,066.5039	$1,066.52	$1,066.55	$1,066.50