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	$143.59	10.168%	$158.1902	$158.19	$158.20	$158.20
Purchase #2	$248.55	13.189%	$281.3313	$281.33	$281.35	$281.30
Purchase #3	$192.71	11.736%	$215.3264	$215.33	$215.35	$215.30
Purchase #4	$216.46	3.173%	$223.3283	$223.33	$223.35	$223.30
Purchase #5	$246.86	8.636%	$268.1788	$268.18	$268.20	$268.20
Purchase #6	$79.44	3.192%	$81.9757	$81.98	$82.00	$82.00
Purchase #7	$47.78	13.193%	$54.0836	$54.08	$54.10	$54.10
7 purchase totals =	$1,175.39		$1,282.4143	$1,282.42	$1,282.55	$1,282.40