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	$86.71	11.415%	$96.6079	$96.61	$96.60	$96.60
Purchase #2	$28.49	12.375%	$32.0156	$32.02	$32.00	$32.00
Purchase #3	$11.39	7.720%	$12.2693	$12.27	$12.25	$12.30
Purchase #4	$174.92	9.676%	$191.8453	$191.85	$191.85	$191.80
Purchase #5	$246.76	11.380%	$274.8413	$274.84	$274.85	$274.80
Purchase #6	$106.46	3.228%	$109.8965	$109.90	$109.90	$109.90
Purchase #7	$232.64	6.781%	$248.4153	$248.42	$248.40	$248.40
7 purchase totals =	$887.37		$965.8912	$965.91	$965.85	$965.80