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	$81.71	5.623%	$86.3046	$86.30	$86.30	$86.30
Purchase #2	$236.64	10.839%	$262.2894	$262.29	$262.30	$262.30
Purchase #3	$212.78	11.597%	$237.4561	$237.46	$237.45	$237.50
Purchase #4	$174.83	3.686%	$181.2742	$181.27	$181.25	$181.30
Purchase #5	$84.86	5.754%	$89.7428	$89.74	$89.75	$89.70
Purchase #6	$149.56	8.201%	$161.8254	$161.83	$161.85	$161.80
Purchase #7	$7.35	3.355%	$7.5966	$7.60	$7.60	$7.60
7 purchase totals =	$947.73		$1,026.4891	$1,026.49	$1,026.50	$1,026.50