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	$124.72	12.775%	$140.653	$140.65	$140.65	$140.70
Purchase #2	$162.36	7.209%	$174.0645	$174.06	$174.05	$174.10
Purchase #3	$68.46	5.244%	$72.05	$72.05	$72.05	$72.10
Purchase #4	$84.75	5.800%	$89.6655	$89.67	$89.65	$89.70
Purchase #5	$116.54	6.195%	$123.7597	$123.76	$123.75	$123.80
Purchase #6	$216.37	13.408%	$245.3809	$245.38	$245.40	$245.40
Purchase #7	$49.94	7.649%	$53.7599	$53.76	$53.75	$53.80
7 purchase totals =	$823.14		$899.3335	$899.33	$899.30	$899.60