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	$164.56	6.282%	$174.8977	$174.90	$174.90	$174.90
Purchase #2	$240.97	7.755%	$259.6572	$259.66	$259.65	$259.70
Purchase #3	$25.64	13.234%	$29.0332	$29.03	$29.05	$29.00
Purchase #4	$57.82	3.319%	$59.739	$59.74	$59.75	$59.70
Purchase #5	$98.69	10.846%	$109.3939	$109.39	$109.40	$109.40
Purchase #6	$72.86	7.140%	$78.0622	$78.06	$78.05	$78.10
Purchase #7	$48.30	8.805%	$52.5528	$52.55	$52.55	$52.60
7 purchase totals =	$708.84		$763.3360	$763.33	$763.35	$763.40