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	$115.52	10.201%	$127.3042	$127.30	$127.30	$127.30
Purchase #2	$90.48	7.113%	$96.9158	$96.92	$96.90	$96.90
Purchase #3	$182.29	4.535%	$190.5569	$190.56	$190.55	$190.60
Purchase #4	$191.83	4.384%	$200.2398	$200.24	$200.25	$200.20
Purchase #5	$142.62	7.795%	$153.7372	$153.74	$153.75	$153.70
Purchase #6	$246.81	7.380%	$265.0246	$265.02	$265.00	$265.00
Purchase #7	$87.73	13.143%	$99.2604	$99.26	$99.25	$99.30
7 purchase totals =	$1,057.28		$1,133.0389	$1,133.04	$1,133.00	$1,133.00