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	$81.40	9.628%	$89.2372	$89.24	$89.25	$89.20
Purchase #2	$151.42	13.453%	$171.7905	$171.79	$171.80	$171.80
Purchase #3	$232.98	3.314%	$240.701	$240.70	$240.70	$240.70
Purchase #4	$91.72	4.249%	$95.6172	$95.62	$95.60	$95.60
Purchase #5	$54.57	7.470%	$58.6464	$58.65	$58.65	$58.60
Purchase #6	$176.38	13.478%	$200.1525	$200.15	$200.15	$200.20
Purchase #7	$171.86	9.840%	$188.771	$188.77	$188.75	$188.80
7 purchase totals =	$960.33		$1,044.9158	$1,044.92	$1,044.90	$1,044.90