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	$188.64	12.851%	$212.8821	$212.88	$212.90	$212.90
Purchase #2	$85.87	12.475%	$96.5823	$96.58	$96.60	$96.60
Purchase #3	$158.66	5.597%	$167.5402	$167.54	$167.55	$167.50
Purchase #4	$92.99	5.629%	$98.2244	$98.22	$98.20	$98.20
Purchase #5	$197.36	13.801%	$224.5977	$224.60	$224.60	$224.60
Purchase #6	$53.85	10.791%	$59.661	$59.66	$59.65	$59.70
Purchase #7	$150.79	10.513%	$166.6426	$166.64	$166.65	$166.60
7 purchase totals =	$928.16		$1,026.1303	$1,026.12	$1,026.15	$1,026.10