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	$47.56	12.610%	$53.5573	$53.56	$53.55	$53.60
Purchase #2	$238.64	12.417%	$268.2719	$268.27	$268.25	$268.30
Purchase #3	$96.39	13.651%	$109.5482	$109.55	$109.55	$109.50
Purchase #4	$153.86	9.233%	$168.0659	$168.07	$168.05	$168.10
Purchase #5	$34.52	3.162%	$35.6115	$35.61	$35.60	$35.60
Purchase #6	$219.80	4.316%	$229.2866	$229.29	$229.30	$229.30
Purchase #7	$214.39	10.537%	$236.9803	$236.98	$237.00	$237.00
7 purchase totals =	$1,005.16		$1,101.3217	$1,101.33	$1,101.30	$1,101.40