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	$142.64	8.539%	$154.82	$154.82	$154.80	$154.80
Purchase #2	$79.84	11.511%	$89.0304	$89.03	$89.05	$89.00
Purchase #3	$54.30	13.255%	$61.4975	$61.50	$61.50	$61.50
Purchase #4	$242.88	10.550%	$268.5038	$268.50	$268.50	$268.50
Purchase #5	$59.95	4.696%	$62.7653	$62.77	$62.75	$62.80
Purchase #6	$206.32	11.113%	$229.2483	$229.25	$229.25	$229.20
Purchase #7	$189.35	3.565%	$196.1003	$196.10	$196.10	$196.10
7 purchase totals =	$975.28		$1,061.9656	$1,061.97	$1,061.95	$1,061.90