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	$159.27	8.371%	$172.6025	$172.60	$172.60	$172.60
Purchase #2	$104.88	13.769%	$119.3209	$119.32	$119.30	$119.30
Purchase #3	$189.54	6.814%	$202.4553	$202.46	$202.45	$202.50
Purchase #4	$171.79	7.742%	$185.09	$185.09	$185.10	$185.10
Purchase #5	$142.33	3.429%	$147.2105	$147.21	$147.20	$147.20
Purchase #6	$105.82	5.424%	$111.5597	$111.56	$111.55	$111.60
Purchase #7	$182.44	4.858%	$191.3029	$191.30	$191.30	$191.30
7 purchase totals =	$1,056.07		$1,129.5418	$1,129.54	$1,129.50	$1,129.60