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	$110.60	11.846%	$123.7017	$123.70	$123.70	$123.70
Purchase #2	$35.71	6.466%	$38.019	$38.02	$38.00	$38.00
Purchase #3	$33.30	4.793%	$34.8961	$34.90	$34.90	$34.90
Purchase #4	$195.90	12.145%	$219.6921	$219.69	$219.70	$219.70
Purchase #5	$227.89	7.651%	$245.3259	$245.33	$245.35	$245.30
Purchase #6	$193.62	11.364%	$215.623	$215.62	$215.60	$215.60
Purchase #7	$245.64	7.406%	$263.8321	$263.83	$263.85	$263.80
7 purchase totals =	$1,042.66		$1,141.0899	$1,141.09	$1,141.10	$1,141.00