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	$95.42	4.428%	$99.6452	$99.65	$99.65	$99.60
Purchase #2	$115.41	10.403%	$127.4161	$127.42	$127.40	$127.40
Purchase #3	$152.67	7.723%	$164.4607	$164.46	$164.45	$164.50
Purchase #4	$148.55	5.276%	$156.3875	$156.39	$156.40	$156.40
Purchase #5	$174.35	9.190%	$190.3728	$190.37	$190.35	$190.40
Purchase #6	$46.89	10.562%	$51.8425	$51.84	$51.85	$51.80
Purchase #7	$236.40	3.332%	$244.2768	$244.28	$244.30	$244.30
7 purchase totals =	$969.69		$1,034.4016	$1,034.41	$1,034.40	$1,034.40