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	$22.93	10.304%	$25.2927	$25.29	$25.30	$25.30
Purchase #2	$228.82	3.238%	$236.2292	$236.23	$236.25	$236.20
Purchase #3	$119.56	6.464%	$127.2884	$127.29	$127.30	$127.30
Purchase #4	$216.55	11.479%	$241.4078	$241.41	$241.40	$241.40
Purchase #5	$227.94	7.280%	$244.534	$244.53	$244.55	$244.50
Purchase #6	$38.52	10.711%	$42.6459	$42.65	$42.65	$42.60
Purchase #7	$168.95	11.334%	$188.0988	$188.10	$188.10	$188.10
7 purchase totals =	$1,023.27		$1,105.4968	$1,105.50	$1,105.55	$1,105.40