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	$115.67	3.216%	$119.3899	$119.39	$119.40	$119.40
Purchase #2	$52.59	12.144%	$58.9765	$58.98	$59.00	$59.00
Purchase #3	$105.34	3.773%	$109.3145	$109.31	$109.30	$109.30
Purchase #4	$115.81	4.609%	$121.1477	$121.15	$121.15	$121.10
Purchase #5	$86.74	4.276%	$90.449	$90.45	$90.45	$90.40
Purchase #6	$168.53	7.381%	$180.9692	$180.97	$180.95	$181.00
Purchase #7	$47.95	12.272%	$53.8344	$53.83	$53.85	$53.80
7 purchase totals =	$692.63		$734.0812	$734.08	$734.10	$734.00