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	$72.46	7.764%	$78.0858	$78.09	$78.10	$78.10
Purchase #2	$13.90	8.339%	$15.0591	$15.06	$15.05	$15.10
Purchase #3	$152.29	8.601%	$165.3885	$165.39	$165.40	$165.40
Purchase #4	$194.82	8.694%	$211.7577	$211.76	$211.75	$211.80
Purchase #5	$29.88	12.279%	$33.549	$33.55	$33.55	$33.50
Purchase #6	$237.90	9.737%	$261.0643	$261.06	$261.05	$261.10
Purchase #7	$31.67	5.769%	$33.497	$33.50	$33.50	$33.50
7 purchase totals =	$732.92		$798.4014	$798.41	$798.40	$798.50