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	$183.82	3.586%	$190.4118	$190.41	$190.40	$190.40
Purchase #2	$106.71	7.779%	$115.011	$115.01	$115.00	$115.00
Purchase #3	$72.27	8.772%	$78.6095	$78.61	$78.60	$78.60
Purchase #4	$243.45	4.124%	$253.4899	$253.49	$253.50	$253.50
Purchase #5	$165.32	7.736%	$178.1092	$178.11	$178.10	$178.10
Purchase #6	$189.41	7.643%	$203.8866	$203.89	$203.90	$203.90
Purchase #7	$150.32	7.680%	$161.8646	$161.86	$161.85	$161.90
7 purchase totals =	$1,111.30		$1,181.3826	$1,181.38	$1,181.35	$1,181.40