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	$66.40	11.478%	$74.0214	$74.02	$74.00	$74.00
Purchase #2	$84.63	6.813%	$90.3958	$90.40	$90.40	$90.40
Purchase #3	$72.92	5.215%	$76.7228	$76.72	$76.70	$76.70
Purchase #4	$82.98	4.607%	$86.8029	$86.80	$86.80	$86.80
Purchase #5	$196.44	10.336%	$216.744	$216.74	$216.75	$216.70
Purchase #6	$59.73	13.555%	$67.8264	$67.83	$67.85	$67.80
Purchase #7	$150.96	3.658%	$156.4821	$156.48	$156.50	$156.50
7 purchase totals =	$714.06		$768.9954	$768.99	$769.00	$768.90