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	$171.82	11.590%	$191.7339	$191.73	$191.75	$191.70
Purchase #2	$98.92	10.596%	$109.4016	$109.40	$109.40	$109.40
Purchase #3	$135.32	6.359%	$143.925	$143.93	$143.95	$143.90
Purchase #4	$174.66	5.403%	$184.0969	$184.10	$184.10	$184.10
Purchase #5	$96.41	6.219%	$102.4057	$102.41	$102.40	$102.40
Purchase #6	$190.25	3.171%	$196.2828	$196.28	$196.30	$196.30
Purchase #7	$101.35	9.843%	$111.3259	$111.33	$111.35	$111.30
7 purchase totals =	$968.73		$1,039.1718	$1,039.18	$1,039.25	$1,039.10