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	$205.56	11.334%	$228.8582	$228.86	$228.85	$228.90
Purchase #2	$72.78	7.582%	$78.2982	$78.30	$78.30	$78.30
Purchase #3	$79.70	10.703%	$88.2303	$88.23	$88.25	$88.20
Purchase #4	$236.50	11.370%	$263.3901	$263.39	$263.40	$263.40
Purchase #5	$117.89	11.589%	$131.5523	$131.55	$131.55	$131.60
Purchase #6	$98.46	4.693%	$103.0807	$103.08	$103.10	$103.10
Purchase #7	$111.93	7.462%	$120.2822	$120.28	$120.30	$120.30
7 purchase totals =	$922.82		$1,013.6920	$1,013.69	$1,013.75	$1,013.80