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	$77.91	5.329%	$82.0618	$82.06	$82.05	$82.10
Purchase #2	$11.38	7.851%	$12.2734	$12.27	$12.25	$12.30
Purchase #3	$243.73	12.783%	$274.886	$274.89	$274.90	$274.90
Purchase #4	$101.64	3.399%	$105.0947	$105.09	$105.10	$105.10
Purchase #5	$48.96	12.543%	$55.1011	$55.10	$55.10	$55.10
Purchase #6	$136.68	13.612%	$155.2849	$155.28	$155.30	$155.30
Purchase #7	$133.67	3.298%	$138.0784	$138.08	$138.10	$138.10
7 purchase totals =	$753.97		$822.7803	$822.77	$822.80	$822.90