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	$89.44	3.693%	$92.743	$92.74	$92.75	$92.70
Purchase #2	$172.57	9.623%	$189.1764	$189.18	$189.20	$189.20
Purchase #3	$105.70	5.126%	$111.1182	$111.12	$111.10	$111.10
Purchase #4	$79.78	3.870%	$82.8675	$82.87	$82.85	$82.90
Purchase #5	$143.54	6.182%	$152.4136	$152.41	$152.40	$152.40
Purchase #6	$89.45	10.549%	$98.8861	$98.89	$98.90	$98.90
Purchase #7	$186.89	12.539%	$210.3241	$210.32	$210.30	$210.30
7 purchase totals =	$867.37		$937.5289	$937.53	$937.50	$937.50