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	$54.33	9.203%	$59.33	$59.33	$59.35	$59.30
Purchase #2	$157.49	10.826%	$174.5399	$174.54	$174.55	$174.50
Purchase #3	$97.69	8.135%	$105.6371	$105.64	$105.65	$105.60
Purchase #4	$194.83	3.104%	$200.8775	$200.88	$200.90	$200.90
Purchase #5	$114.88	11.667%	$128.283	$128.28	$128.30	$128.30
Purchase #6	$229.53	4.588%	$240.0608	$240.06	$240.05	$240.10
Purchase #7	$249.30	8.472%	$270.4207	$270.42	$270.40	$270.40
7 purchase totals =	$1,098.05		$1,179.1490	$1,179.15	$1,179.20	$1,179.10