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	$201.73	10.623%	$223.1598	$223.16	$223.15	$223.20
Purchase #2	$100.27	9.618%	$109.914	$109.91	$109.90	$109.90
Purchase #3	$69.55	7.248%	$74.591	$74.59	$74.60	$74.60
Purchase #4	$154.36	5.420%	$162.7263	$162.73	$162.75	$162.70
Purchase #5	$49.96	9.357%	$54.6348	$54.63	$54.65	$54.60
Purchase #6	$153.82	7.195%	$164.8873	$164.89	$164.90	$164.90
Purchase #7	$173.92	12.626%	$195.8791	$195.88	$195.90	$195.90
7 purchase totals =	$903.61		$985.7923	$985.79	$985.85	$985.80