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	$193.72	7.253%	$207.7705	$207.77	$207.75	$207.80
Purchase #2	$68.59	5.645%	$72.4619	$72.46	$72.45	$72.50
Purchase #3	$211.68	12.587%	$238.3242	$238.32	$238.30	$238.30
Purchase #4	$174.32	4.488%	$182.1435	$182.14	$182.15	$182.10
Purchase #5	$154.98	5.579%	$163.6263	$163.63	$163.65	$163.60
Purchase #6	$102.91	6.739%	$109.8451	$109.85	$109.85	$109.80
Purchase #7	$59.82	12.538%	$67.3202	$67.32	$67.30	$67.30
7 purchase totals =	$966.02		$1,041.4917	$1,041.49	$1,041.45	$1,041.40