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	$27.29	3.676%	$28.2932	$28.29	$28.30	$28.30
Purchase #2	$142.48	8.144%	$154.0836	$154.08	$154.10	$154.10
Purchase #3	$194.79	7.118%	$208.6552	$208.66	$208.65	$208.70
Purchase #4	$89.33	10.431%	$98.648	$98.65	$98.65	$98.60
Purchase #5	$40.80	12.535%	$45.9143	$45.91	$45.90	$45.90
Purchase #6	$233.57	11.779%	$261.0822	$261.08	$261.10	$261.10
Purchase #7	$210.35	4.280%	$219.353	$219.35	$219.35	$219.40
7 purchase totals =	$938.61		$1,016.0295	$1,016.02	$1,016.05	$1,016.10