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	$180.89	8.494%	$196.2548	$196.25	$196.25	$196.30
Purchase #2	$84.63	13.630%	$96.1651	$96.17	$96.15	$96.20
Purchase #3	$166.86	9.334%	$182.4347	$182.43	$182.45	$182.40
Purchase #4	$221.78	8.155%	$239.8662	$239.87	$239.85	$239.90
Purchase #5	$72.97	8.160%	$78.9244	$78.92	$78.90	$78.90
Purchase #6	$165.72	5.477%	$174.7965	$174.80	$174.80	$174.80
Purchase #7	$200.67	9.565%	$219.8641	$219.86	$219.85	$219.90
7 purchase totals =	$1,093.52		$1,188.3058	$1,188.30	$1,188.25	$1,188.40