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	$194.32	11.363%	$216.4006	$216.40	$216.40	$216.40
Purchase #2	$70.63	11.743%	$78.9241	$78.92	$78.90	$78.90
Purchase #3	$5.80	4.592%	$6.0663	$6.07	$6.05	$6.10
Purchase #4	$101.63	7.564%	$109.3173	$109.32	$109.30	$109.30
Purchase #5	$211.26	5.263%	$222.3786	$222.38	$222.40	$222.40
Purchase #6	$62.53	12.414%	$70.2925	$70.29	$70.30	$70.30
Purchase #7	$82.71	6.709%	$88.259	$88.26	$88.25	$88.30
7 purchase totals =	$728.88		$791.6384	$791.64	$791.60	$791.70