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	$180.40	7.504%	$193.9372	$193.94	$193.95	$193.90
Purchase #2	$42.57	7.739%	$45.8645	$45.86	$45.85	$45.90
Purchase #3	$162.25	13.596%	$184.3095	$184.31	$184.30	$184.30
Purchase #4	$85.46	7.157%	$91.5764	$91.58	$91.60	$91.60
Purchase #5	$163.58	11.274%	$182.022	$182.02	$182.00	$182.00
Purchase #6	$71.85	9.543%	$78.7066	$78.71	$78.70	$78.70
Purchase #7	$64.94	12.127%	$72.8153	$72.82	$72.80	$72.80
7 purchase totals =	$771.05		$849.2315	$849.24	$849.20	$849.20