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	$98.62	13.547%	$111.9801	$111.98	$112.00	$112.00
Purchase #2	$57.28	4.199%	$59.6852	$59.69	$59.70	$59.70
Purchase #3	$158.30	7.632%	$170.3815	$170.38	$170.40	$170.40
Purchase #4	$46.91	4.344%	$48.9478	$48.95	$48.95	$48.90
Purchase #5	$218.77	6.529%	$233.0535	$233.05	$233.05	$233.10
Purchase #6	$106.57	13.445%	$120.8983	$120.90	$120.90	$120.90
Purchase #7	$96.26	9.619%	$105.5192	$105.52	$105.50	$105.50
7 purchase totals =	$782.71		$850.4656	$850.47	$850.50	$850.50