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	$176.31	4.837%	$184.8381	$184.84	$184.85	$184.80
Purchase #2	$197.54	12.432%	$222.0982	$222.10	$222.10	$222.10
Purchase #3	$54.64	6.116%	$57.9818	$57.98	$58.00	$58.00
Purchase #4	$55.41	12.666%	$62.4282	$62.43	$62.45	$62.40
Purchase #5	$7.27	4.452%	$7.5937	$7.59	$7.60	$7.60
Purchase #6	$55.38	12.291%	$62.1868	$62.19	$62.20	$62.20
Purchase #7	$232.50	7.708%	$250.4211	$250.42	$250.40	$250.40
7 purchase totals =	$779.05		$847.5479	$847.55	$847.60	$847.50