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	$191.65	9.546%	$209.9449	$209.94	$209.95	$209.90
Purchase #2	$238.38	10.465%	$263.3265	$263.33	$263.35	$263.30
Purchase #3	$127.42	11.626%	$142.2338	$142.23	$142.25	$142.20
Purchase #4	$162.99	3.298%	$168.3654	$168.37	$168.35	$168.40
Purchase #5	$229.67	13.591%	$260.8844	$260.88	$260.90	$260.90
Purchase #6	$225.50	4.372%	$235.3589	$235.36	$235.35	$235.40
Purchase #7	$83.52	7.453%	$89.7447	$89.74	$89.75	$89.70
7 purchase totals =	$1,259.13		$1,369.8586	$1,369.85	$1,369.90	$1,369.80