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	$230.38	3.581%	$238.6299	$238.63	$238.65	$238.60
Purchase #2	$164.86	12.253%	$185.0603	$185.06	$185.05	$185.10
Purchase #3	$58.91	6.643%	$62.8234	$62.82	$62.80	$62.80
Purchase #4	$134.31	5.802%	$142.1027	$142.10	$142.10	$142.10
Purchase #5	$170.96	5.727%	$180.7509	$180.75	$180.75	$180.80
Purchase #6	$46.90	7.327%	$50.3364	$50.34	$50.35	$50.30
Purchase #7	$190.62	4.242%	$198.7061	$198.71	$198.70	$198.70
7 purchase totals =	$996.94		$1,058.4097	$1,058.41	$1,058.40	$1,058.40