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	$162.92	5.254%	$171.4798	$171.48	$171.50	$171.50
Purchase #2	$124.77	3.159%	$128.7115	$128.71	$128.70	$128.70
Purchase #3	$65.59	10.284%	$72.3353	$72.34	$72.35	$72.30
Purchase #4	$73.73	5.846%	$78.0403	$78.04	$78.05	$78.00
Purchase #5	$96.30	7.241%	$103.2731	$103.27	$103.25	$103.30
Purchase #6	$223.60	6.128%	$237.3022	$237.30	$237.30	$237.30
Purchase #7	$235.66	10.482%	$260.3619	$260.36	$260.35	$260.40
7 purchase totals =	$982.57		$1,051.5041	$1,051.50	$1,051.50	$1,051.50