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	$44.53	3.730%	$46.191	$46.19	$46.20	$46.20
Purchase #2	$112.33	13.328%	$127.3013	$127.30	$127.30	$127.30
Purchase #3	$83.88	4.523%	$87.6739	$87.67	$87.65	$87.70
Purchase #4	$78.69	12.347%	$88.4059	$88.41	$88.40	$88.40
Purchase #5	$191.25	4.726%	$200.2885	$200.29	$200.30	$200.30
Purchase #6	$21.94	3.632%	$22.7369	$22.74	$22.75	$22.70
Purchase #7	$137.34	3.236%	$141.7843	$141.78	$141.80	$141.80
7 purchase totals =	$669.96		$714.3818	$714.38	$714.40	$714.40