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	$103.78	10.768%	$114.955	$114.96	$114.95	$115.00
Purchase #2	$57.76	5.173%	$60.7479	$60.75	$60.75	$60.70
Purchase #3	$91.76	13.173%	$103.8475	$103.85	$103.85	$103.80
Purchase #4	$142.73	6.748%	$152.3614	$152.36	$152.35	$152.40
Purchase #5	$129.97	9.356%	$142.13	$142.13	$142.15	$142.10
Purchase #6	$65.76	6.260%	$69.8766	$69.88	$69.90	$69.90
Purchase #7	$19.77	7.352%	$21.2235	$21.22	$21.20	$21.20
7 purchase totals =	$611.53		$665.1419	$665.15	$665.15	$665.10