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	$233.84	7.329%	$250.9781	$250.98	$251.00	$251.00
Purchase #2	$73.85	8.776%	$80.3311	$80.33	$80.35	$80.30
Purchase #3	$99.99	11.545%	$111.5338	$111.53	$111.55	$111.50
Purchase #4	$240.68	11.578%	$268.5459	$268.55	$268.55	$268.50
Purchase #5	$151.47	9.469%	$165.8127	$165.81	$165.80	$165.80
Purchase #6	$126.66	11.543%	$141.2804	$141.28	$141.30	$141.30
Purchase #7	$168.58	10.372%	$186.0651	$186.07	$186.05	$186.10
7 purchase totals =	$1,095.07		$1,204.5471	$1,204.55	$1,204.60	$1,204.50