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	$84.65	13.645%	$96.2005	$96.20	$96.20	$96.20
Purchase #2	$140.91	4.394%	$147.1016	$147.10	$147.10	$147.10
Purchase #3	$35.78	7.860%	$38.5923	$38.59	$38.60	$38.60
Purchase #4	$34.83	8.194%	$37.684	$37.68	$37.70	$37.70
Purchase #5	$84.74	7.451%	$91.054	$91.05	$91.05	$91.10
Purchase #6	$144.46	8.469%	$156.6943	$156.69	$156.70	$156.70
Purchase #7	$67.87	6.648%	$72.382	$72.38	$72.40	$72.40
7 purchase totals =	$593.24		$639.7087	$639.69	$639.75	$639.80