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	$181.38	3.750%	$188.1818	$188.18	$188.20	$188.20
Purchase #2	$171.57	9.759%	$188.3135	$188.31	$188.30	$188.30
Purchase #3	$175.50	13.704%	$199.5505	$199.55	$199.55	$199.60
Purchase #4	$142.56	3.645%	$147.7563	$147.76	$147.75	$147.80
Purchase #5	$175.71	5.732%	$185.7817	$185.78	$185.80	$185.80
Purchase #6	$43.62	4.537%	$45.599	$45.60	$45.60	$45.60
Purchase #7	$102.30	3.565%	$105.947	$105.95	$105.95	$105.90
7 purchase totals =	$992.64		$1,061.1298	$1,061.13	$1,061.15	$1,061.20