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	$25.66	10.114%	$28.2553	$28.26	$28.25	$28.30
Purchase #2	$215.42	6.363%	$229.1272	$229.13	$229.15	$229.10
Purchase #3	$230.61	11.604%	$257.37	$257.37	$257.35	$257.40
Purchase #4	$78.76	13.587%	$89.4611	$89.46	$89.45	$89.50
Purchase #5	$169.45	13.540%	$192.3935	$192.39	$192.40	$192.40
Purchase #6	$184.32	12.615%	$207.572	$207.57	$207.55	$207.60
Purchase #7	$199.90	9.336%	$218.5627	$218.56	$218.55	$218.60
7 purchase totals =	$1,104.12		$1,222.7418	$1,222.74	$1,222.70	$1,222.90