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	$210.75	10.668%	$233.2328	$233.23	$233.25	$233.20
Purchase #2	$80.55	13.656%	$91.5499	$91.55	$91.55	$91.50
Purchase #3	$12.46	3.823%	$12.9363	$12.94	$12.95	$12.90
Purchase #4	$51.37	7.274%	$55.1067	$55.11	$55.10	$55.10
Purchase #5	$99.57	3.751%	$103.3049	$103.30	$103.30	$103.30
Purchase #6	$38.55	11.169%	$42.8556	$42.86	$42.85	$42.90
Purchase #7	$223.42	8.500%	$242.4107	$242.41	$242.40	$242.40
7 purchase totals =	$716.67		$781.3969	$781.40	$781.40	$781.30