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	$90.91	5.632%	$96.0301	$96.03	$96.05	$96.00
Purchase #2	$58.94	9.344%	$64.4474	$64.45	$64.45	$64.40
Purchase #3	$114.87	3.324%	$118.6883	$118.69	$118.70	$118.70
Purchase #4	$172.97	7.520%	$185.9773	$185.98	$186.00	$186.00
Purchase #5	$63.74	6.460%	$67.8576	$67.86	$67.85	$67.90
Purchase #6	$148.46	13.516%	$168.5259	$168.53	$168.55	$168.50
Purchase #7	$24.58	11.127%	$27.315	$27.32	$27.30	$27.30
7 purchase totals =	$674.47		$728.8416	$728.86	$728.90	$728.80