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	$86.48	11.408%	$96.3456	$96.35	$96.35	$96.30
Purchase #2	$7.56	3.512%	$7.8255	$7.83	$7.85	$7.80
Purchase #3	$36.90	6.496%	$39.297	$39.30	$39.30	$39.30
Purchase #4	$206.88	6.320%	$219.9548	$219.95	$219.95	$220.00
Purchase #5	$128.86	7.841%	$138.9639	$138.96	$138.95	$139.00
Purchase #6	$50.92	7.274%	$54.6239	$54.62	$54.60	$54.60
Purchase #7	$81.82	10.622%	$90.5109	$90.51	$90.50	$90.50
7 purchase totals =	$599.42		$647.5216	$647.52	$647.50	$647.50