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	$138.68	10.424%	$153.136	$153.14	$153.15	$153.10
Purchase #2	$51.27	8.818%	$55.791	$55.79	$55.80	$55.80
Purchase #3	$77.71	6.353%	$82.6469	$82.65	$82.65	$82.60
Purchase #4	$101.56	12.383%	$114.1362	$114.14	$114.15	$114.10
Purchase #5	$128.94	13.582%	$146.4526	$146.45	$146.45	$146.50
Purchase #6	$238.83	4.729%	$250.1243	$250.12	$250.10	$250.10
Purchase #7	$170.35	9.345%	$186.2692	$186.27	$186.25	$186.30
7 purchase totals =	$907.34		$988.5562	$988.56	$988.55	$988.50