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	$200.58	5.129%	$210.8677	$210.87	$210.85	$210.90
Purchase #2	$80.35	6.831%	$85.8387	$85.84	$85.85	$85.80
Purchase #3	$49.79	6.457%	$53.0049	$53.00	$53.00	$53.00
Purchase #4	$167.55	7.664%	$180.391	$180.39	$180.40	$180.40
Purchase #5	$214.49	10.190%	$236.3465	$236.35	$236.35	$236.30
Purchase #6	$84.29	9.308%	$92.1357	$92.14	$92.15	$92.10
Purchase #7	$137.95	4.609%	$144.3081	$144.31	$144.30	$144.30
7 purchase totals =	$935.00		$1,002.8926	$1,002.90	$1,002.90	$1,002.80