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	$179.63	9.562%	$196.8062	$196.81	$196.80	$196.80
Purchase #2	$142.74	12.192%	$160.1429	$160.14	$160.15	$160.10
Purchase #3	$211.32	3.763%	$219.272	$219.27	$219.25	$219.30
Purchase #4	$169.64	7.224%	$181.8948	$181.89	$181.90	$181.90
Purchase #5	$139.65	5.565%	$147.4215	$147.42	$147.40	$147.40
Purchase #6	$6.81	8.355%	$7.379	$7.38	$7.40	$7.40
Purchase #7	$88.89	8.606%	$96.5399	$96.54	$96.55	$96.50
7 purchase totals =	$938.68		$1,009.4563	$1,009.45	$1,009.45	$1,009.40