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	$29.69	6.271%	$31.5519	$31.55	$31.55	$31.60
Purchase #2	$238.46	10.272%	$262.9546	$262.95	$262.95	$263.00
Purchase #3	$79.90	12.581%	$89.9522	$89.95	$89.95	$90.00
Purchase #4	$173.71	10.331%	$191.656	$191.66	$191.65	$191.70
Purchase #5	$162.93	7.269%	$174.7734	$174.77	$174.75	$174.80
Purchase #6	$138.98	9.596%	$152.3165	$152.32	$152.30	$152.30
Purchase #7	$195.35	5.240%	$205.5863	$205.59	$205.60	$205.60
7 purchase totals =	$1,019.02		$1,108.7909	$1,108.79	$1,108.75	$1,109.00