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	$156.61	11.415%	$174.487	$174.49	$174.50	$174.50
Purchase #2	$218.54	9.865%	$240.099	$240.10	$240.10	$240.10
Purchase #3	$235.33	6.678%	$251.0453	$251.05	$251.05	$251.00
Purchase #4	$80.60	11.152%	$89.5885	$89.59	$89.60	$89.60
Purchase #5	$200.37	11.177%	$222.7654	$222.77	$222.75	$222.80
Purchase #6	$7.40	6.366%	$7.8711	$7.87	$7.85	$7.90
Purchase #7	$58.26	12.257%	$65.4009	$65.40	$65.40	$65.40
7 purchase totals =	$957.11		$1,051.2572	$1,051.27	$1,051.25	$1,051.30