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	$124.55	3.143%	$128.4646	$128.46	$128.45	$128.50
Purchase #2	$181.88	4.757%	$190.532	$190.53	$190.55	$190.50
Purchase #3	$28.91	7.729%	$31.1445	$31.14	$31.15	$31.10
Purchase #4	$193.48	3.439%	$200.1338	$200.13	$200.15	$200.10
Purchase #5	$197.48	12.552%	$222.2677	$222.27	$222.25	$222.30
Purchase #6	$178.30	11.345%	$198.5281	$198.53	$198.55	$198.50
Purchase #7	$155.80	4.844%	$163.347	$163.35	$163.35	$163.30
7 purchase totals =	$1,060.40		$1,134.4177	$1,134.41	$1,134.45	$1,134.30