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	$200.54	3.144%	$206.845	$206.85	$206.85	$206.80
Purchase #2	$52.46	4.351%	$54.7425	$54.74	$54.75	$54.70
Purchase #3	$121.87	7.295%	$130.7604	$130.76	$130.75	$130.80
Purchase #4	$41.59	3.348%	$42.9824	$42.98	$43.00	$43.00
Purchase #5	$152.93	5.156%	$160.8151	$160.82	$160.80	$160.80
Purchase #6	$147.87	13.799%	$168.2746	$168.27	$168.25	$168.30
Purchase #7	$51.80	13.861%	$58.98	$58.98	$59.00	$59.00
7 purchase totals =	$769.06		$823.4000	$823.40	$823.40	$823.40