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	$92.45	11.808%	$103.3665	$103.37	$103.35	$103.40
Purchase #2	$64.71	7.492%	$69.5581	$69.56	$69.55	$69.60
Purchase #3	$168.33	12.714%	$189.7315	$189.73	$189.75	$189.70
Purchase #4	$50.82	12.192%	$57.016	$57.02	$57.00	$57.00
Purchase #5	$114.43	7.131%	$122.59	$122.59	$122.60	$122.60
Purchase #6	$135.77	4.774%	$142.2517	$142.25	$142.25	$142.30
Purchase #7	$72.91	12.399%	$81.9501	$81.95	$81.95	$82.00
7 purchase totals =	$699.42		$766.4639	$766.47	$766.45	$766.60