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	$201.50	4.225%	$210.0134	$210.01	$210.00	$210.00
Purchase #2	$151.27	3.326%	$156.3012	$156.30	$156.30	$156.30
Purchase #3	$70.86	10.474%	$78.2819	$78.28	$78.30	$78.30
Purchase #4	$37.96	10.788%	$42.0551	$42.06	$42.05	$42.10
Purchase #5	$192.74	9.871%	$211.7654	$211.77	$211.75	$211.80
Purchase #6	$80.48	12.693%	$90.6953	$90.70	$90.70	$90.70
Purchase #7	$81.41	4.579%	$85.1378	$85.14	$85.15	$85.10
7 purchase totals =	$816.22		$874.2501	$874.26	$874.25	$874.30