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	$244.57	13.263%	$277.0073	$277.01	$277.00	$277.00
Purchase #2	$85.60	13.292%	$96.978	$96.98	$97.00	$97.00
Purchase #3	$62.71	3.674%	$65.014	$65.01	$65.00	$65.00
Purchase #4	$119.53	13.255%	$135.3737	$135.37	$135.35	$135.40
Purchase #5	$204.72	12.155%	$229.6037	$229.60	$229.60	$229.60
Purchase #6	$242.46	12.769%	$273.4197	$273.42	$273.40	$273.40
Purchase #7	$85.54	5.149%	$89.9445	$89.94	$89.95	$89.90
7 purchase totals =	$1,045.13		$1,167.3409	$1,167.33	$1,167.30	$1,167.30