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	$169.98	7.278%	$182.3511	$182.35	$182.35	$182.40
Purchase #2	$176.62	7.523%	$189.9071	$189.91	$189.90	$189.90
Purchase #3	$48.44	13.520%	$54.9891	$54.99	$55.00	$55.00
Purchase #4	$80.54	10.637%	$89.107	$89.11	$89.10	$89.10
Purchase #5	$57.66	8.500%	$62.5611	$62.56	$62.55	$62.60
Purchase #6	$196.66	6.333%	$209.1145	$209.11	$209.10	$209.10
Purchase #7	$189.46	5.304%	$199.509	$199.51	$199.50	$199.50
7 purchase totals =	$919.36		$987.5389	$987.54	$987.50	$987.60