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	$143.55	6.284%	$152.5707	$152.57	$152.55	$152.60
Purchase #2	$97.59	6.552%	$103.9841	$103.98	$104.00	$104.00
Purchase #3	$96.62	3.157%	$99.6703	$99.67	$99.65	$99.70
Purchase #4	$70.35	12.424%	$79.0903	$79.09	$79.10	$79.10
Purchase #5	$35.72	4.385%	$37.2863	$37.29	$37.30	$37.30
Purchase #6	$156.41	10.280%	$172.4889	$172.49	$172.50	$172.50
Purchase #7	$129.96	11.760%	$145.2433	$145.24	$145.25	$145.20
7 purchase totals =	$730.20		$790.3339	$790.33	$790.35	$790.40