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	$190.72	10.192%	$210.1582	$210.16	$210.15	$210.20
Purchase #2	$174.59	8.264%	$189.0181	$189.02	$189.00	$189.00
Purchase #3	$47.45	13.449%	$53.8316	$53.83	$53.85	$53.80
Purchase #4	$226.36	8.633%	$245.9017	$245.90	$245.90	$245.90
Purchase #5	$21.55	13.237%	$24.4026	$24.40	$24.40	$24.40
Purchase #6	$70.36	11.645%	$78.5534	$78.55	$78.55	$78.60
Purchase #7	$213.56	12.352%	$239.9389	$239.94	$239.95	$239.90
7 purchase totals =	$944.59		$1,041.8045	$1,041.80	$1,041.80	$1,041.80