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	$130.65	3.403%	$135.096	$135.10	$135.10	$135.10
Purchase #2	$79.25	12.803%	$89.3964	$89.40	$89.40	$89.40
Purchase #3	$249.48	3.212%	$257.4933	$257.49	$257.50	$257.50
Purchase #4	$108.71	13.397%	$123.2739	$123.27	$123.25	$123.30
Purchase #5	$228.76	4.374%	$238.766	$238.77	$238.75	$238.80
Purchase #6	$206.32	7.692%	$222.1901	$222.19	$222.20	$222.20
Purchase #7	$108.45	4.106%	$112.903	$112.90	$112.90	$112.90
7 purchase totals =	$1,111.62		$1,179.1187	$1,179.12	$1,179.10	$1,179.20