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	$218.70	9.807%	$240.1479	$240.15	$240.15	$240.10
Purchase #2	$131.92	7.740%	$142.1306	$142.13	$142.15	$142.10
Purchase #3	$35.86	6.312%	$38.1235	$38.12	$38.10	$38.10
Purchase #4	$211.60	9.445%	$231.5856	$231.59	$231.60	$231.60
Purchase #5	$176.73	11.379%	$196.8401	$196.84	$196.85	$196.80
Purchase #6	$109.35	6.456%	$116.4096	$116.41	$116.40	$116.40
Purchase #7	$207.56	4.257%	$216.3958	$216.40	$216.40	$216.40
7 purchase totals =	$1,091.72		$1,181.6331	$1,181.64	$1,181.65	$1,181.50