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	$231.89	4.109%	$241.4184	$241.42	$241.40	$241.40
Purchase #2	$124.31	10.499%	$137.3613	$137.36	$137.35	$137.40
Purchase #3	$67.90	6.447%	$72.2775	$72.28	$72.30	$72.30
Purchase #4	$73.95	5.819%	$78.2532	$78.25	$78.25	$78.30
Purchase #5	$141.28	13.122%	$159.8188	$159.82	$159.80	$159.80
Purchase #6	$218.48	5.171%	$229.7776	$229.78	$229.80	$229.80
Purchase #7	$92.37	8.617%	$100.3295	$100.33	$100.35	$100.30
7 purchase totals =	$950.18		$1,019.2363	$1,019.24	$1,019.25	$1,019.30