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	$86.85	4.661%	$90.8981	$90.90	$90.90	$90.90
Purchase #2	$180.31	4.808%	$188.9793	$188.98	$189.00	$189.00
Purchase #3	$82.40	4.158%	$85.8262	$85.83	$85.85	$85.80
Purchase #4	$178.57	4.146%	$185.9735	$185.97	$185.95	$186.00
Purchase #5	$167.56	13.205%	$189.6863	$189.69	$189.70	$189.70
Purchase #6	$171.51	4.622%	$179.4372	$179.44	$179.45	$179.40
Purchase #7	$146.26	6.319%	$155.5022	$155.50	$155.50	$155.50
7 purchase totals =	$1,013.46		$1,076.3028	$1,076.31	$1,076.35	$1,076.30