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	$46.74	12.573%	$52.6166	$52.62	$52.60	$52.60
Purchase #2	$162.32	5.346%	$170.9976	$171.00	$171.00	$171.00
Purchase #3	$105.53	9.754%	$115.8234	$115.82	$115.80	$115.80
Purchase #4	$246.65	7.635%	$265.4817	$265.48	$265.50	$265.50
Purchase #5	$177.58	10.835%	$196.8208	$196.82	$196.80	$196.80
Purchase #6	$180.53	8.835%	$196.4798	$196.48	$196.50	$196.50
Purchase #7	$98.70	11.276%	$109.8294	$109.83	$109.85	$109.80
7 purchase totals =	$1,018.05		$1,108.0493	$1,108.05	$1,108.05	$1,108.00