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	$112.63	10.219%	$124.1397	$124.14	$124.15	$124.10
Purchase #2	$220.28	12.708%	$248.2732	$248.27	$248.25	$248.30
Purchase #3	$85.58	6.653%	$91.2736	$91.27	$91.25	$91.30
Purchase #4	$45.33	12.331%	$50.9196	$50.92	$50.90	$50.90
Purchase #5	$215.46	10.520%	$238.1264	$238.13	$238.15	$238.10
Purchase #6	$23.95	6.450%	$25.4948	$25.49	$25.50	$25.50
Purchase #7	$217.38	9.676%	$238.4137	$238.41	$238.40	$238.40
7 purchase totals =	$920.61		$1,016.6410	$1,016.63	$1,016.60	$1,016.60