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	$48.62	9.127%	$53.0575	$53.06	$53.05	$53.10
Purchase #2	$89.37	5.525%	$94.3077	$94.31	$94.30	$94.30
Purchase #3	$68.62	4.300%	$71.5707	$71.57	$71.55	$71.60
Purchase #4	$204.52	5.312%	$215.3841	$215.38	$215.40	$215.40
Purchase #5	$183.90	3.850%	$190.9802	$190.98	$191.00	$191.00
Purchase #6	$152.40	8.476%	$165.3174	$165.32	$165.30	$165.30
Purchase #7	$197.75	8.489%	$214.537	$214.54	$214.55	$214.50
7 purchase totals =	$945.18		$1,005.1546	$1,005.16	$1,005.15	$1,005.20