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	$146.63	3.489%	$151.7459	$151.75	$151.75	$151.70
Purchase #2	$81.67	10.833%	$90.5173	$90.52	$90.50	$90.50
Purchase #3	$198.45	3.861%	$206.1122	$206.11	$206.10	$206.10
Purchase #4	$96.56	7.128%	$103.4428	$103.44	$103.45	$103.40
Purchase #5	$113.59	12.287%	$127.5468	$127.55	$127.55	$127.50
Purchase #6	$157.38	4.457%	$164.3944	$164.39	$164.40	$164.40
Purchase #7	$155.74	7.812%	$167.9064	$167.91	$167.90	$167.90
7 purchase totals =	$950.02		$1,011.6658	$1,011.67	$1,011.65	$1,011.50