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	$90.88	4.178%	$94.677	$94.68	$94.70	$94.70
Purchase #2	$168.49	12.531%	$189.6035	$189.60	$189.60	$189.60
Purchase #3	$216.38	7.823%	$233.3074	$233.31	$233.30	$233.30
Purchase #4	$216.39	3.335%	$223.6066	$223.61	$223.60	$223.60
Purchase #5	$79.25	7.585%	$85.2611	$85.26	$85.25	$85.30
Purchase #6	$156.68	11.148%	$174.1467	$174.15	$174.15	$174.10
Purchase #7	$175.38	7.759%	$188.9877	$188.99	$189.00	$189.00
7 purchase totals =	$1,103.45		$1,189.5900	$1,189.60	$1,189.60	$1,189.60