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	$174.94	3.608%	$181.2518	$181.25	$181.25	$181.30
Purchase #2	$81.43	9.102%	$88.8418	$88.84	$88.85	$88.80
Purchase #3	$106.38	9.767%	$116.7701	$116.77	$116.75	$116.80
Purchase #4	$98.39	7.230%	$105.5036	$105.50	$105.50	$105.50
Purchase #5	$168.42	12.351%	$189.2216	$189.22	$189.20	$189.20
Purchase #6	$98.30	13.637%	$111.7052	$111.71	$111.70	$111.70
Purchase #7	$54.83	6.417%	$58.3484	$58.35	$58.35	$58.30
7 purchase totals =	$782.69		$851.6425	$851.64	$851.60	$851.60