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	$70.28	3.332%	$72.6217	$72.62	$72.60	$72.60
Purchase #2	$240.63	3.708%	$249.5526	$249.55	$249.55	$249.60
Purchase #3	$147.32	4.608%	$154.1085	$154.11	$154.10	$154.10
Purchase #4	$157.46	4.640%	$164.7661	$164.77	$164.75	$164.80
Purchase #5	$74.90	13.871%	$85.2894	$85.29	$85.30	$85.30
Purchase #6	$161.55	3.130%	$166.6065	$166.61	$166.60	$166.60
Purchase #7	$226.81	9.508%	$248.3751	$248.38	$248.40	$248.40
7 purchase totals =	$1,078.95		$1,141.3199	$1,141.33	$1,141.30	$1,141.40