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	$148.59	4.355%	$155.0611	$155.06	$155.05	$155.10
Purchase #2	$249.96	9.340%	$273.3063	$273.31	$273.30	$273.30
Purchase #3	$227.65	7.309%	$244.2889	$244.29	$244.30	$244.30
Purchase #4	$153.70	11.667%	$171.6322	$171.63	$171.65	$171.60
Purchase #5	$37.39	12.698%	$42.1378	$42.14	$42.15	$42.10
Purchase #6	$161.63	11.133%	$179.6243	$179.62	$179.60	$179.60
Purchase #7	$99.29	8.270%	$107.5013	$107.50	$107.50	$107.50
7 purchase totals =	$1,078.21		$1,173.5519	$1,173.55	$1,173.55	$1,173.50