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	$95.33	10.447%	$105.2891	$105.29	$105.30	$105.30
Purchase #2	$100.61	12.328%	$113.0132	$113.01	$113.00	$113.00
Purchase #3	$109.48	12.152%	$122.784	$122.78	$122.80	$122.80
Purchase #4	$223.32	5.538%	$235.6875	$235.69	$235.70	$235.70
Purchase #5	$243.88	7.173%	$261.3735	$261.37	$261.35	$261.40
Purchase #6	$80.55	7.399%	$86.5099	$86.51	$86.50	$86.50
Purchase #7	$167.69	7.486%	$180.2433	$180.24	$180.25	$180.20
7 purchase totals =	$1,020.86		$1,104.9005	$1,104.89	$1,104.90	$1,104.90