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	$182.87	6.621%	$194.9778	$194.98	$195.00	$195.00
Purchase #2	$85.81	5.263%	$90.3262	$90.33	$90.35	$90.30
Purchase #3	$124.40	13.632%	$141.3582	$141.36	$141.35	$141.40
Purchase #4	$126.52	5.458%	$133.4255	$133.43	$133.45	$133.40
Purchase #5	$165.83	10.705%	$183.5821	$183.58	$183.60	$183.60
Purchase #6	$72.72	7.295%	$78.0249	$78.02	$78.00	$78.00
Purchase #7	$51.92	11.386%	$57.8316	$57.83	$57.85	$57.80
7 purchase totals =	$810.07		$879.5263	$879.53	$879.60	$879.50