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	$101.76	8.765%	$110.6793	$110.68	$110.70	$110.70
Purchase #2	$120.56	3.238%	$124.4637	$124.46	$124.45	$124.50
Purchase #3	$57.81	4.652%	$60.4993	$60.50	$60.50	$60.50
Purchase #4	$224.88	8.476%	$243.9408	$243.94	$243.95	$243.90
Purchase #5	$125.85	4.275%	$131.2301	$131.23	$131.25	$131.20
Purchase #6	$183.83	11.424%	$204.8307	$204.83	$204.85	$204.80
Purchase #7	$164.68	12.729%	$185.6421	$185.64	$185.65	$185.60
7 purchase totals =	$979.37		$1,061.2860	$1,061.28	$1,061.35	$1,061.20