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	$146.42	6.816%	$156.4	$156.40	$156.40	$156.40
Purchase #2	$180.62	5.360%	$190.3012	$190.30	$190.30	$190.30
Purchase #3	$96.95	6.646%	$103.3933	$103.39	$103.40	$103.40
Purchase #4	$7.93	5.489%	$8.3653	$8.37	$8.35	$8.40
Purchase #5	$221.59	10.626%	$245.1362	$245.14	$245.15	$245.10
Purchase #6	$186.38	13.118%	$210.8293	$210.83	$210.85	$210.80
Purchase #7	$133.46	6.464%	$142.0869	$142.09	$142.10	$142.10
7 purchase totals =	$973.35		$1,056.5122	$1,056.52	$1,056.55	$1,056.50