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	$69.25	13.830%	$78.8273	$78.83	$78.85	$78.80
Purchase #2	$163.75	4.603%	$171.2874	$171.29	$171.30	$171.30
Purchase #3	$183.35	4.195%	$191.0415	$191.04	$191.05	$191.00
Purchase #4	$149.65	6.255%	$159.0106	$159.01	$159.00	$159.00
Purchase #5	$135.53	3.234%	$139.913	$139.91	$139.90	$139.90
Purchase #6	$6.56	10.295%	$7.2354	$7.24	$7.25	$7.20
Purchase #7	$41.88	7.518%	$45.0285	$45.03	$45.05	$45.00
7 purchase totals =	$749.97		$792.3437	$792.35	$792.40	$792.20