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	$158.43	7.461%	$170.2505	$170.25	$170.25	$170.30
Purchase #2	$182.62	4.628%	$191.0717	$191.07	$191.05	$191.10
Purchase #3	$189.40	3.811%	$196.618	$196.62	$196.60	$196.60
Purchase #4	$205.71	12.432%	$231.2839	$231.28	$231.30	$231.30
Purchase #5	$240.37	9.814%	$263.9599	$263.96	$263.95	$264.00
Purchase #6	$104.91	6.606%	$111.8404	$111.84	$111.85	$111.80
Purchase #7	$62.62	4.451%	$65.4072	$65.41	$65.40	$65.40
7 purchase totals =	$1,144.06		$1,230.4316	$1,230.43	$1,230.40	$1,230.50