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	$187.62	4.781%	$196.5901	$196.59	$196.60	$196.60
Purchase #2	$189.50	4.728%	$198.4596	$198.46	$198.45	$198.50
Purchase #3	$75.80	10.224%	$83.5498	$83.55	$83.55	$83.50
Purchase #4	$135.45	9.356%	$148.1227	$148.12	$148.10	$148.10
Purchase #5	$101.98	11.865%	$114.0799	$114.08	$114.10	$114.10
Purchase #6	$75.60	6.241%	$80.3182	$80.32	$80.30	$80.30
Purchase #7	$118.43	4.816%	$124.1336	$124.13	$124.15	$124.10
7 purchase totals =	$884.38		$945.2539	$945.25	$945.25	$945.20