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	$96.91	12.753%	$109.2689	$109.27	$109.25	$109.30
Purchase #2	$18.67	11.673%	$20.8493	$20.85	$20.85	$20.80
Purchase #3	$120.39	8.260%	$130.3342	$130.33	$130.35	$130.30
Purchase #4	$127.59	10.844%	$141.4259	$141.43	$141.45	$141.40
Purchase #5	$82.57	3.425%	$85.398	$85.40	$85.40	$85.40
Purchase #6	$162.56	12.139%	$182.2932	$182.29	$182.30	$182.30
Purchase #7	$50.76	4.629%	$53.1097	$53.11	$53.10	$53.10
7 purchase totals =	$659.45		$722.6792	$722.68	$722.70	$722.60