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	$182.58	7.696%	$196.6314	$196.63	$196.65	$196.60
Purchase #2	$37.26	7.836%	$40.1797	$40.18	$40.20	$40.20
Purchase #3	$233.69	13.150%	$264.4202	$264.42	$264.40	$264.40
Purchase #4	$58.82	5.782%	$62.221	$62.22	$62.20	$62.20
Purchase #5	$168.32	9.450%	$184.2262	$184.23	$184.25	$184.20
Purchase #6	$78.61	13.856%	$89.5022	$89.50	$89.50	$89.50
Purchase #7	$96.86	12.864%	$109.3201	$109.32	$109.30	$109.30
7 purchase totals =	$856.14		$946.5008	$946.50	$946.50	$946.40