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	$164.86	13.650%	$187.3634	$187.36	$187.35	$187.40
Purchase #2	$101.46	7.832%	$109.4063	$109.41	$109.40	$109.40
Purchase #3	$31.35	12.433%	$35.2477	$35.25	$35.25	$35.20
Purchase #4	$166.30	9.650%	$182.348	$182.35	$182.35	$182.30
Purchase #5	$57.31	12.618%	$64.5414	$64.54	$64.55	$64.50
Purchase #6	$238.34	8.834%	$259.395	$259.40	$259.40	$259.40
Purchase #7	$211.50	13.609%	$240.283	$240.28	$240.30	$240.30
7 purchase totals =	$971.12		$1,078.5848	$1,078.59	$1,078.60	$1,078.50