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	$165.65	13.403%	$187.8521	$187.85	$187.85	$187.90
Purchase #2	$98.99	4.358%	$103.304	$103.30	$103.30	$103.30
Purchase #3	$245.39	6.510%	$261.3649	$261.36	$261.35	$261.40
Purchase #4	$118.37	7.660%	$127.4371	$127.44	$127.45	$127.40
Purchase #5	$204.43	3.289%	$211.1537	$211.15	$211.15	$211.20
Purchase #6	$158.96	5.216%	$167.2514	$167.25	$167.25	$167.30
Purchase #7	$58.25	11.800%	$65.1235	$65.12	$65.10	$65.10
7 purchase totals =	$1,050.04		$1,123.4867	$1,123.47	$1,123.45	$1,123.60