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	$21.25	4.860%	$22.2828	$22.28	$22.30	$22.30
Purchase #2	$172.91	12.369%	$194.2972	$194.30	$194.30	$194.30
Purchase #3	$185.32	3.278%	$191.3948	$191.39	$191.40	$191.40
Purchase #4	$141.89	11.657%	$158.4301	$158.43	$158.45	$158.40
Purchase #5	$102.70	6.464%	$109.3385	$109.34	$109.35	$109.30
Purchase #6	$206.96	8.109%	$223.7424	$223.74	$223.75	$223.70
Purchase #7	$54.30	8.364%	$58.8417	$58.84	$58.85	$58.80
7 purchase totals =	$885.33		$958.3275	$958.32	$958.40	$958.20