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	$32.56	3.666%	$33.7536	$33.75	$33.75	$33.80
Purchase #2	$79.29	12.558%	$89.2472	$89.25	$89.25	$89.20
Purchase #3	$106.32	7.685%	$114.4907	$114.49	$114.50	$114.50
Purchase #4	$62.26	11.851%	$69.6384	$69.64	$69.65	$69.60
Purchase #5	$107.86	10.784%	$119.4916	$119.49	$119.50	$119.50
Purchase #6	$100.49	13.851%	$114.4089	$114.41	$114.40	$114.40
Purchase #7	$178.40	7.184%	$191.2163	$191.22	$191.20	$191.20
7 purchase totals =	$667.18		$732.2467	$732.25	$732.25	$732.20