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	$110.36	9.301%	$120.6246	$120.62	$120.60	$120.60
Purchase #2	$167.50	6.390%	$178.2033	$178.20	$178.20	$178.20
Purchase #3	$167.27	7.366%	$179.5911	$179.59	$179.60	$179.60
Purchase #4	$95.98	3.586%	$99.4218	$99.42	$99.40	$99.40
Purchase #5	$203.51	3.317%	$210.2604	$210.26	$210.25	$210.30
Purchase #6	$238.56	11.789%	$266.6838	$266.68	$266.70	$266.70
Purchase #7	$81.26	11.581%	$90.6707	$90.67	$90.65	$90.70
7 purchase totals =	$1,064.44		$1,145.4557	$1,145.44	$1,145.40	$1,145.50