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	$187.94	9.782%	$206.3243	$206.32	$206.30	$206.30
Purchase #2	$211.29	9.171%	$230.6674	$230.67	$230.65	$230.70
Purchase #3	$80.77	10.397%	$89.1677	$89.17	$89.15	$89.20
Purchase #4	$127.76	13.621%	$145.1622	$145.16	$145.15	$145.20
Purchase #5	$57.31	11.486%	$63.8926	$63.89	$63.90	$63.90
Purchase #6	$167.96	11.646%	$187.5206	$187.52	$187.50	$187.50
Purchase #7	$134.52	13.398%	$152.543	$152.54	$152.55	$152.50
7 purchase totals =	$967.55		$1,075.2778	$1,075.27	$1,075.20	$1,075.30