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	$139.43	10.664%	$154.2988	$154.30	$154.30	$154.30
Purchase #2	$56.32	5.465%	$59.3979	$59.40	$59.40	$59.40
Purchase #3	$187.53	9.420%	$205.1953	$205.20	$205.20	$205.20
Purchase #4	$190.42	13.263%	$215.6754	$215.68	$215.70	$215.70
Purchase #5	$135.76	10.771%	$150.3827	$150.38	$150.40	$150.40
Purchase #6	$125.82	13.786%	$143.1655	$143.17	$143.15	$143.20
Purchase #7	$81.27	6.782%	$86.7817	$86.78	$86.80	$86.80
7 purchase totals =	$916.55		$1,014.8973	$1,014.91	$1,014.95	$1,015.00