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	$152.67	11.588%	$170.3614	$170.36	$170.35	$170.40
Purchase #2	$89.81	10.407%	$99.1565	$99.16	$99.15	$99.20
Purchase #3	$152.78	7.831%	$164.7442	$164.74	$164.75	$164.70
Purchase #4	$223.83	6.263%	$237.8485	$237.85	$237.85	$237.80
Purchase #5	$94.60	5.457%	$99.7623	$99.76	$99.75	$99.80
Purchase #6	$109.45	12.486%	$123.1159	$123.12	$123.10	$123.10
Purchase #7	$149.27	8.241%	$161.5713	$161.57	$161.55	$161.60
7 purchase totals =	$972.41		$1,056.5601	$1,056.56	$1,056.50	$1,056.60