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	$139.85	8.237%	$151.3694	$151.37	$151.35	$151.40
Purchase #2	$183.46	9.499%	$200.8869	$200.89	$200.90	$200.90
Purchase #3	$218.67	4.525%	$228.5648	$228.56	$228.55	$228.60
Purchase #4	$65.93	10.794%	$73.0465	$73.05	$73.05	$73.00
Purchase #5	$83.25	4.579%	$87.062	$87.06	$87.05	$87.10
Purchase #6	$69.66	3.451%	$72.064	$72.06	$72.05	$72.10
Purchase #7	$96.88	12.865%	$109.3436	$109.34	$109.35	$109.30
7 purchase totals =	$857.70		$922.3372	$922.33	$922.30	$922.40