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	$90.46	4.113%	$94.1806	$94.18	$94.20	$94.20
Purchase #2	$189.45	4.829%	$198.5985	$198.60	$198.60	$198.60
Purchase #3	$130.89	9.156%	$142.8743	$142.87	$142.85	$142.90
Purchase #4	$160.28	3.610%	$166.0661	$166.07	$166.05	$166.10
Purchase #5	$239.88	5.597%	$253.3061	$253.31	$253.30	$253.30
Purchase #6	$53.26	11.513%	$59.3918	$59.39	$59.40	$59.40
Purchase #7	$181.64	5.720%	$192.0298	$192.03	$192.05	$192.00
7 purchase totals =	$1,045.86		$1,106.4472	$1,106.45	$1,106.45	$1,106.50