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	$172.96	12.623%	$194.7927	$194.79	$194.80	$194.80
Purchase #2	$124.79	7.291%	$133.8884	$133.89	$133.90	$133.90
Purchase #3	$48.33	9.692%	$53.0141	$53.01	$53.00	$53.00
Purchase #4	$40.39	6.119%	$42.8615	$42.86	$42.85	$42.90
Purchase #5	$54.36	9.227%	$59.3758	$59.38	$59.40	$59.40
Purchase #6	$56.57	3.391%	$58.4883	$58.49	$58.50	$58.50
Purchase #7	$229.53	4.457%	$239.7602	$239.76	$239.75	$239.80
7 purchase totals =	$726.93		$782.1810	$782.18	$782.20	$782.30