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	$94.63	9.436%	$103.5593	$103.56	$103.55	$103.60
Purchase #2	$101.72	4.145%	$105.9363	$105.94	$105.95	$105.90
Purchase #3	$172.91	10.323%	$190.7595	$190.76	$190.75	$190.80
Purchase #4	$39.85	9.651%	$43.6959	$43.70	$43.70	$43.70
Purchase #5	$165.76	3.220%	$171.0975	$171.10	$171.10	$171.10
Purchase #6	$197.84	9.782%	$217.1927	$217.19	$217.20	$217.20
Purchase #7	$198.43	10.155%	$218.5806	$218.58	$218.60	$218.60
7 purchase totals =	$971.14		$1,050.8218	$1,050.83	$1,050.85	$1,050.90