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	$136.25	4.518%	$142.4058	$142.41	$142.40	$142.40
Purchase #2	$200.30	6.283%	$212.8848	$212.88	$212.90	$212.90
Purchase #3	$75.38	11.196%	$83.8195	$83.82	$83.80	$83.80
Purchase #4	$222.85	6.254%	$236.787	$236.79	$236.80	$236.80
Purchase #5	$91.52	13.432%	$103.813	$103.81	$103.80	$103.80
Purchase #6	$234.48	11.467%	$261.3678	$261.37	$261.35	$261.40
Purchase #7	$103.58	7.816%	$111.6758	$111.68	$111.70	$111.70
7 purchase totals =	$1,064.36		$1,152.7537	$1,152.76	$1,152.75	$1,152.80