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	$29.27	9.144%	$31.9464	$31.95	$31.95	$31.90
Purchase #2	$233.47	11.667%	$260.7089	$260.71	$260.70	$260.70
Purchase #3	$91.59	7.873%	$98.8009	$98.80	$98.80	$98.80
Purchase #4	$203.41	3.199%	$209.9171	$209.92	$209.90	$209.90
Purchase #5	$40.39	12.309%	$45.3616	$45.36	$45.35	$45.40
Purchase #6	$245.73	12.421%	$276.2521	$276.25	$276.25	$276.30
Purchase #7	$72.59	11.663%	$81.0562	$81.06	$81.05	$81.10
7 purchase totals =	$916.45		$1,004.0432	$1,004.05	$1,004.00	$1,004.10