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	$68.93	7.824%	$74.3231	$74.32	$74.30	$74.30
Purchase #2	$71.40	13.843%	$81.2839	$81.28	$81.30	$81.30
Purchase #3	$250.75	3.416%	$259.3156	$259.32	$259.30	$259.30
Purchase #4	$233.29	13.532%	$264.8588	$264.86	$264.85	$264.90
Purchase #5	$250.76	6.280%	$266.5077	$266.51	$266.50	$266.50
Purchase #6	$88.84	12.462%	$99.9112	$99.91	$99.90	$99.90
Purchase #7	$89.26	11.570%	$99.5874	$99.59	$99.60	$99.60
7 purchase totals =	$1,053.23		$1,145.7877	$1,145.79	$1,145.75	$1,145.80