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	$141.37	8.114%	$152.8408	$152.84	$152.85	$152.80
Purchase #2	$249.43	10.257%	$275.014	$275.01	$275.00	$275.00
Purchase #3	$48.46	10.425%	$53.512	$53.51	$53.50	$53.50
Purchase #4	$67.82	6.646%	$72.3273	$72.33	$72.35	$72.30
Purchase #5	$65.55	13.666%	$74.5081	$74.51	$74.50	$74.50
Purchase #6	$118.93	8.343%	$128.8523	$128.85	$128.85	$128.90
Purchase #7	$93.53	11.153%	$103.9614	$103.96	$103.95	$104.00
7 purchase totals =	$785.09		$861.0159	$861.01	$861.00	$861.00