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	$147.96	13.245%	$167.5573	$167.56	$167.55	$167.60
Purchase #2	$57.31	10.856%	$63.5316	$63.53	$63.55	$63.50
Purchase #3	$90.96	10.367%	$100.3898	$100.39	$100.40	$100.40
Purchase #4	$112.46	9.551%	$123.2011	$123.20	$123.20	$123.20
Purchase #5	$243.33	6.661%	$259.5382	$259.54	$259.55	$259.50
Purchase #6	$147.37	4.351%	$153.7821	$153.78	$153.80	$153.80
Purchase #7	$228.57	5.327%	$240.7459	$240.75	$240.75	$240.70
7 purchase totals =	$1,027.96		$1,108.7460	$1,108.75	$1,108.80	$1,108.70