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	$176.47	11.225%	$196.2788	$196.28	$196.30	$196.30
Purchase #2	$245.33	12.729%	$276.5581	$276.56	$276.55	$276.60
Purchase #3	$98.29	11.279%	$109.3761	$109.38	$109.40	$109.40
Purchase #4	$19.45	4.316%	$20.2895	$20.29	$20.30	$20.30
Purchase #5	$211.90	10.131%	$233.3676	$233.37	$233.35	$233.40
Purchase #6	$89.57	11.155%	$99.5615	$99.56	$99.55	$99.60
Purchase #7	$248.60	5.393%	$262.007	$262.01	$262.00	$262.00
7 purchase totals =	$1,089.61		$1,197.4386	$1,197.45	$1,197.45	$1,197.60