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	$104.41	4.670%	$109.2859	$109.29	$109.30	$109.30
Purchase #2	$36.39	13.308%	$41.2328	$41.23	$41.25	$41.20
Purchase #3	$120.85	5.607%	$127.6261	$127.63	$127.65	$127.60
Purchase #4	$77.47	5.337%	$81.6046	$81.60	$81.60	$81.60
Purchase #5	$52.28	6.675%	$55.7697	$55.77	$55.75	$55.80
Purchase #6	$193.46	10.544%	$213.8584	$213.86	$213.85	$213.90
Purchase #7	$141.36	10.168%	$155.7335	$155.73	$155.75	$155.70
7 purchase totals =	$726.22		$785.1110	$785.11	$785.15	$785.10