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	$151.49	4.524%	$158.3434	$158.34	$158.35	$158.30
Purchase #2	$71.72	9.586%	$78.5951	$78.60	$78.60	$78.60
Purchase #3	$54.31	7.165%	$58.2013	$58.20	$58.20	$58.20
Purchase #4	$237.38	13.112%	$268.5053	$268.51	$268.50	$268.50
Purchase #5	$174.36	11.798%	$194.931	$194.93	$194.95	$194.90
Purchase #6	$181.57	8.421%	$196.86	$196.86	$196.85	$196.90
Purchase #7	$181.64	4.706%	$190.188	$190.19	$190.20	$190.20
7 purchase totals =	$1,052.47		$1,145.6241	$1,145.63	$1,145.65	$1,145.60