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	$164.94	7.223%	$176.8536	$176.85	$176.85	$176.90
Purchase #2	$154.80	7.442%	$166.3202	$166.32	$166.30	$166.30
Purchase #3	$167.37	9.414%	$183.1262	$183.13	$183.15	$183.10
Purchase #4	$73.46	7.122%	$78.6918	$78.69	$78.70	$78.70
Purchase #5	$114.84	13.524%	$130.371	$130.37	$130.35	$130.40
Purchase #6	$167.87	3.844%	$174.3229	$174.32	$174.30	$174.30
Purchase #7	$206.94	7.413%	$222.2805	$222.28	$222.30	$222.30
7 purchase totals =	$1,050.22		$1,131.9662	$1,131.96	$1,131.95	$1,132.00