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	$185.76	13.181%	$210.245	$210.25	$210.25	$210.20
Purchase #2	$40.44	4.834%	$42.3949	$42.39	$42.40	$42.40
Purchase #3	$93.46	3.326%	$96.5685	$96.57	$96.55	$96.60
Purchase #4	$134.50	6.135%	$142.7516	$142.75	$142.75	$142.80
Purchase #5	$113.39	6.758%	$121.0529	$121.05	$121.05	$121.10
Purchase #6	$91.36	13.756%	$103.9275	$103.93	$103.95	$103.90
Purchase #7	$99.53	10.205%	$109.687	$109.69	$109.70	$109.70
7 purchase totals =	$758.44		$826.6274	$826.63	$826.65	$826.70