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	$82.70	9.662%	$90.6905	$90.69	$90.70	$90.70
Purchase #2	$93.46	13.874%	$106.4266	$106.43	$106.45	$106.40
Purchase #3	$163.73	6.441%	$174.2758	$174.28	$174.30	$174.30
Purchase #4	$127.67	11.790%	$142.7223	$142.72	$142.70	$142.70
Purchase #5	$55.67	9.666%	$61.0511	$61.05	$61.05	$61.10
Purchase #6	$105.94	3.451%	$109.596	$109.60	$109.60	$109.60
Purchase #7	$61.77	10.188%	$68.0631	$68.06	$68.05	$68.10
7 purchase totals =	$690.94		$752.8254	$752.83	$752.85	$752.90