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	$79.27	3.518%	$82.0587	$82.06	$82.05	$82.10
Purchase #2	$178.85	3.543%	$185.1867	$185.19	$185.20	$185.20
Purchase #3	$197.68	12.339%	$222.0717	$222.07	$222.05	$222.10
Purchase #4	$250.80	11.307%	$279.158	$279.16	$279.15	$279.20
Purchase #5	$198.96	6.716%	$212.3222	$212.32	$212.30	$212.30
Purchase #6	$165.85	13.862%	$188.8401	$188.84	$188.85	$188.80
Purchase #7	$31.55	12.649%	$35.5408	$35.54	$35.55	$35.50
7 purchase totals =	$1,102.96		$1,205.1782	$1,205.18	$1,205.15	$1,205.20