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	$185.28	5.821%	$196.0651	$196.07	$196.05	$196.10
Purchase #2	$168.25	12.847%	$189.8651	$189.87	$189.85	$189.90
Purchase #3	$206.71	3.264%	$213.457	$213.46	$213.45	$213.50
Purchase #4	$16.81	7.390%	$18.0523	$18.05	$18.05	$18.10
Purchase #5	$164.72	12.459%	$185.2425	$185.24	$185.25	$185.20
Purchase #6	$165.37	5.199%	$173.9676	$173.97	$173.95	$174.00
Purchase #7	$77.91	7.561%	$83.8008	$83.80	$83.80	$83.80
7 purchase totals =	$985.05		$1,060.4504	$1,060.46	$1,060.40	$1,060.60