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	$133.27	11.203%	$148.2002	$148.20	$148.20	$148.20
Purchase #2	$178.50	5.383%	$188.1087	$188.11	$188.10	$188.10
Purchase #3	$161.70	7.184%	$173.3165	$173.32	$173.30	$173.30
Purchase #4	$209.29	4.253%	$218.1911	$218.19	$218.20	$218.20
Purchase #5	$163.29	5.144%	$171.6896	$171.69	$171.70	$171.70
Purchase #6	$36.38	5.822%	$38.498	$38.50	$38.50	$38.50
Purchase #7	$119.83	3.362%	$123.8587	$123.86	$123.85	$123.90
7 purchase totals =	$1,002.26		$1,061.8628	$1,061.87	$1,061.85	$1,061.90