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	$99.78	10.415%	$110.1721	$110.17	$110.15	$110.20
Purchase #2	$202.56	10.121%	$223.0611	$223.06	$223.05	$223.10
Purchase #3	$168.39	4.420%	$175.8328	$175.83	$175.85	$175.80
Purchase #4	$121.27	5.633%	$128.1011	$128.10	$128.10	$128.10
Purchase #5	$63.75	9.708%	$69.9389	$69.94	$69.95	$69.90
Purchase #6	$205.59	8.659%	$223.392	$223.39	$223.40	$223.40
Purchase #7	$79.38	3.627%	$82.2591	$82.26	$82.25	$82.30
7 purchase totals =	$940.72		$1,012.7571	$1,012.75	$1,012.75	$1,012.80