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	$102.73	8.788%	$111.7579	$111.76	$111.75	$111.80
Purchase #2	$6.62	11.129%	$7.3567	$7.36	$7.35	$7.40
Purchase #3	$68.67	6.157%	$72.898	$72.90	$72.90	$72.90
Purchase #4	$70.55	11.624%	$78.7507	$78.75	$78.75	$78.80
Purchase #5	$209.93	13.355%	$237.9662	$237.97	$237.95	$238.00
Purchase #6	$226.54	12.627%	$255.1452	$255.15	$255.15	$255.10
Purchase #7	$88.30	3.502%	$91.3923	$91.39	$91.40	$91.40
7 purchase totals =	$773.34		$855.2670	$855.28	$855.25	$855.40