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	$128.43	10.556%	$141.9871	$141.99	$142.00	$142.00
Purchase #2	$226.90	7.673%	$244.31	$244.31	$244.30	$244.30
Purchase #3	$166.81	4.760%	$174.7502	$174.75	$174.75	$174.80
Purchase #4	$75.64	4.414%	$78.9787	$78.98	$79.00	$79.00
Purchase #5	$84.25	6.294%	$89.5527	$89.55	$89.55	$89.60
Purchase #6	$248.72	13.406%	$282.0634	$282.06	$282.05	$282.10
Purchase #7	$48.60	9.588%	$53.2598	$53.26	$53.25	$53.30
7 purchase totals =	$979.35		$1,064.9019	$1,064.90	$1,064.90	$1,065.10