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	$177.58	10.658%	$196.5065	$196.51	$196.50	$196.50
Purchase #2	$148.39	9.582%	$162.6087	$162.61	$162.60	$162.60
Purchase #3	$51.36	13.208%	$58.1436	$58.14	$58.15	$58.10
Purchase #4	$67.56	5.580%	$71.3298	$71.33	$71.35	$71.30
Purchase #5	$19.78	5.469%	$20.8618	$20.86	$20.85	$20.90
Purchase #6	$168.57	7.554%	$181.3038	$181.30	$181.30	$181.30
Purchase #7	$182.76	10.836%	$202.5639	$202.56	$202.55	$202.60
7 purchase totals =	$816.00		$893.3181	$893.31	$893.30	$893.30