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	$97.36	3.632%	$100.8961	$100.90	$100.90	$100.90
Purchase #2	$186.29	13.614%	$211.6515	$211.65	$211.65	$211.70
Purchase #3	$206.33	5.102%	$216.857	$216.86	$216.85	$216.90
Purchase #4	$27.30	9.494%	$29.8919	$29.89	$29.90	$29.90
Purchase #5	$151.30	7.578%	$162.7655	$162.77	$162.75	$162.80
Purchase #6	$134.53	6.166%	$142.8251	$142.83	$142.85	$142.80
Purchase #7	$141.83	10.316%	$156.4612	$156.46	$156.45	$156.50
7 purchase totals =	$944.94		$1,021.3483	$1,021.36	$1,021.35	$1,021.50