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	$53.71	11.133%	$59.6895	$59.69	$59.70	$59.70
Purchase #2	$179.28	10.598%	$198.2801	$198.28	$198.30	$198.30
Purchase #3	$147.80	5.586%	$156.0561	$156.06	$156.05	$156.10
Purchase #4	$111.87	10.323%	$123.4183	$123.42	$123.40	$123.40
Purchase #5	$169.94	13.794%	$193.3815	$193.38	$193.40	$193.40
Purchase #6	$170.37	9.227%	$186.09	$186.09	$186.10	$186.10
Purchase #7	$25.74	9.279%	$28.1284	$28.13	$28.15	$28.10
7 purchase totals =	$858.71		$945.0439	$945.05	$945.10	$945.10