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	$201.89	5.170%	$212.3277	$212.33	$212.35	$212.30
Purchase #2	$68.26	5.612%	$72.0908	$72.09	$72.10	$72.10
Purchase #3	$219.31	5.413%	$231.1813	$231.18	$231.20	$231.20
Purchase #4	$178.43	4.295%	$186.0936	$186.09	$186.10	$186.10
Purchase #5	$239.56	12.379%	$269.2151	$269.22	$269.20	$269.20
Purchase #6	$95.58	10.483%	$105.5997	$105.60	$105.60	$105.60
Purchase #7	$32.90	7.486%	$35.3629	$35.36	$35.35	$35.40
7 purchase totals =	$1,035.93		$1,111.8711	$1,111.87	$1,111.90	$1,111.90