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	$184.32	8.199%	$199.4324	$199.43	$199.45	$199.40
Purchase #2	$172.98	9.330%	$189.119	$189.12	$189.10	$189.10
Purchase #3	$17.59	11.828%	$19.6705	$19.67	$19.65	$19.70
Purchase #4	$26.34	5.299%	$27.7358	$27.74	$27.75	$27.70
Purchase #5	$56.78	4.132%	$59.1261	$59.13	$59.15	$59.10
Purchase #6	$91.94	8.586%	$99.834	$99.83	$99.85	$99.80
Purchase #7	$203.96	12.488%	$229.4305	$229.43	$229.45	$229.40
7 purchase totals =	$753.91		$824.3483	$824.35	$824.40	$824.20