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	$94.75	6.435%	$100.8472	$100.85	$100.85	$100.80
Purchase #2	$163.28	6.793%	$174.3716	$174.37	$174.35	$174.40
Purchase #3	$58.69	9.149%	$64.0595	$64.06	$64.05	$64.10
Purchase #4	$87.33	7.794%	$94.1365	$94.14	$94.15	$94.10
Purchase #5	$86.86	3.469%	$89.8732	$89.87	$89.85	$89.90
Purchase #6	$31.31	8.109%	$33.8489	$33.85	$33.85	$33.80
Purchase #7	$187.84	12.571%	$211.4534	$211.45	$211.45	$211.50
7 purchase totals =	$710.06		$768.5903	$768.59	$768.55	$768.60